魔术方法

__construct()， __destruct()， __call()， __callStatic()， __get()， __set()， __isset()， __unset()， __sleep()， __wakeup()， __toString()， __invoke()， __set_state()， __clone() 和 __debugInfo() 等方法在 PHP 中被称为魔术方法（Magic methods）。在命名自己的类方法时不能使用这些方法名，除非是想使用其魔术功能。

Caution

PHP 将所有以 __（两个下划线）开头的类方法保留为魔术方法。所以在定义类方法时，除了上述魔术方法，建议不要以 __ 为前缀。

__sleep() 和 __wakeup()

public __sleep ( void ) : array
__wakeup ( void ) : void

serialize() 函数会检查类中是否存在一个魔术方法 __sleep()。如果存在，该方法会先被调用，然后才执行序列化操作。此功能可以用于清理对象，并返回一个包含对象中所有应被序列化的变量名称的数组。如果该方法未返回任何内容，则 NULL 被序列化，并产生一个 E_NOTICE 级别的错误。

Note:

__sleep() 不能返回父类的私有成员的名字。这样做会产生一个 E_NOTICE 级别的错误。可以用 Serializable 接口来替代。

__sleep() 方法常用于提交未提交的数据，或类似的清理操作。同时，如果有一些很大的对象，但不需要全部保存，这个功能就很好用。

与之相反，unserialize() 会检查是否存在一个 __wakeup() 方法。如果存在，则会先调用 __wakeup 方法，预先准备对象需要的资源。

__wakeup() 经常用在反序列化操作中，例如重新建立数据库连接，或执行其它初始化操作。

Example #1 Sleep 和 wakeup

<?php
class Connection 
{
    protected $link;
    private $server, $username, $password, $db;
    
    public function __construct($server, $username, $password, $db)
    {
        $this->server = $server;
        $this->username = $username;
        $this->password = $password;
        $this->db = $db;
        $this->connect();
    }
    
    private function connect()
    {
        $this->link = mysql_connect($this->server, $this->username, $this->password);
        mysql_select_db($this->db, $this->link);
    }
    
    public function __sleep()
    {
        return array('server', 'username', 'password', 'db');
    }
    
    public function __wakeup()
    {
        $this->connect();
    }
}
?>

__toString()

public __toString ( void ) : string

__toString() 方法用于一个类被当成字符串时应怎样回应。例如 echo $obj; 应该显示些什么。此方法必须返回一个字符串，否则将发出一条 E_RECOVERABLE_ERROR 级别的致命错误。

Warning

不能在 __toString() 方法中抛出异常。这么做会导致致命错误。

Example #2 简单示例

<?php
// Declare a simple class
class TestClass
{
    public $foo;

    public function __construct($foo) 
    {
        $this->foo = $foo;
    }

    public function __toString() {
        return $this->foo;
    }
}

$class = new TestClass('Hello');
echo $class;
?>

以上例程会输出：

Hello

需要指出的是在 PHP 5.2.0 之前，__toString() 方法只有在直接使用于 echo 或 print 时才能生效。PHP 5.2.0 之后，则可以在任何字符串环境生效（例如通过 printf()，使用 %s 修饰符），但不能用于非字符串环境（如使用 %d 修饰符）。自 PHP 5.2.0 起，如果将一个未定义 __toString() 方法的对象转换为字符串，会产生 E_RECOVERABLE_ERROR 级别的错误。

__invoke()

__invoke ([ $... ] ) : mixed

当尝试以调用函数的方式调用一个对象时，__invoke() 方法会被自动调用。

Note:

本特性只在 PHP 5.3.0 及以上版本有效。

Example #3 使用 __invoke()

<?php
class CallableClass 
{
    function __invoke($x) {
        var_dump($x);
    }
}
$obj = new CallableClass;
$obj(5);
var_dump(is_callable($obj));
?>

以上例程会输出：

int(5)
bool(true)

__set_state()

static __set_state ( array $properties ) : object

自 PHP 5.1.0 起当调用 var_export() 导出类时，此静态 方法会被调用。

本方法的唯一参数是一个数组，其中包含按 array('property' => value, ...) 格式排列的类属性。

Example #4 使用 __set_state()>（PHP 5.1.0 起）

<?php

class A
{
    public $var1;
    public $var2;

    public static function __set_state($an_array) // As of PHP 5.1.0
    {
        $obj = new A;
        $obj->var1 = $an_array['var1'];
        $obj->var2 = $an_array['var2'];
        return $obj;
    }
}

$a = new A;
$a->var1 = 5;
$a->var2 = 'foo';

eval('$b = ' . var_export($a, true) . ';'); // $b = A::__set_state(array(
                                            //    'var1' => 5,
                                            //    'var2' => 'foo',
                                            // ));
var_dump($b);

?>

以上例程会输出：

object(A)#2 (2) {
  ["var1"]=>
  int(5)
  ["var2"]=>
  string(3) "foo"
}

__debugInfo()

__debugInfo ( void ) : array

This method is called by var_dump() when dumping an object to get the properties that should be shown. If the method isn't defined on an object, then all public, protected and private properties will be shown.

This feature was added in PHP 5.6.0.

Example #5 Using __debugInfo()

<?php
class C {
    private $prop;

    public function __construct($val) {
        $this->prop = $val;
    }

    public function __debugInfo() {
        return [
            'propSquared' => $this->prop ** 2,
        ];
    }
}

var_dump(new C(42));
?>

以上例程会输出：

object(C)#1 (1) {
  ["propSquared"]=>
  int(1764)
}

User Contributed Notes

daniel dot peder at gmail dot com 30-Apr-2018 09:29
http://sandbox.onlinephpfunctions.com/code/4d2cc3648aed58c0dad90c7868173a4775e5ba0c

IMHO a bug or need feature change

providing a object as a array index doesn't try to us __toString() method so some volatile object identifier is used to index the array, which is breaking any persistency. Type hinting solves that, but while other than "string" type hinting doesn't work on ob jects, the automatic conversion to string should be very intuitive.

PS: tried to submit bug, but withot patch the bugs are ignored, unfortunately, I don't C coding

<?php

class shop_product_id {
   
    protected $shop_name;
    protected $product_id;
   
    function __construct($shop_name,$product_id){
        $this->shop_name = $shop_name;
        $this->product_id = $product_id;
    }

    function __toString(){
        return $this->shop_name . ':' . $this->product_id;
    }
}

$shop_name = 'Shop_A';
$product_id = 123;
$demo_id = $shop_name . ':' . $product_id;
$demo_name = 'Some product in shop A';

$all_products = [ $demo_id => $demo_name ];
$pid = new shop_product_id( $shop_name, $product_id );

echo "with type hinting: ";
echo ($demo_name === $all_products[(string)$pid]) ? "ok" : "fail";
echo "\n";

echo "without type hinting: ";
echo ($demo_name === $all_products[$pid]) ?  "ok" : "fail";
echo "\n";
kguest at php dot net 30-May-2017 01:27
__debugInfo  is also utilised when calling print_r on an object:

$ cat test.php
<?php
class FooQ {

     private $bar = '';

     public function __construct($val) {

         $this->bar = $val;
     }

     public function __debugInfo()
     {
         return ['_bar' => $this->bar];
     }
}
$fooq = new FooQ("q");
print_r ($fooq);

$ php test.php
FooQ Object
(
    [_bar] => q
)
$
ryan dot jentzsch at gmail dot com 15-Sep-2016 07:04
PHP 7+ solves a problem with __invoke noted about 4 yrs ago:

<?php
class a {
    function __construct() { }
    function __invoke() { echo("Invoked\n"); }
}

$a = new a();
$a();
// Output: Invoked

class b {
    private $x;

    function __construct() {
        $this->x = new a();
        ($this->x)();  // Works in PHP 7+
        // $this->x(); // Will blow up in your face: undefined method b::x
    }
}

$b = new b();
// Output: Invoked
smiley at HELLOSPAMBOT dot chillerlan dot net 09-Jan-2016 04:30
A simple API wrapper, using __call() and the PHP 5.6 "..." token.
http://php.net/manual/functions.arguments.php#functions.variable-arg-list

<?php
namespace Example;

use Exception;
use ReflectionClass;
use SomeApiInterface;
use SomeHttpClient;
use SomeEndpointHandler;

/**
 * Class SomeApiWrapper
 *
 * @method SomeEndpointHandler method1(MethodParams $param1)
 * @method SomeEndpointHandler method2(MethodParams $param1, AuthParams $param2 = null)
 * ...
 * @method SomeEndpointHandler method42()
 */
class SomeApiWrapper{

    /**
     * @var \SomeHttpClient
     */
    private $httpClient;

    /**
     * @var array
     */
    private $methodMap = [];

    /**
     * SomeApiWrapper constructor.
     */
    public function __construct(){
        $this->mapApiMethods();
        $this->httpClient = new SomeHttpClient();
    }

    /**
     * The API is flat and has ~ 150 endpoints, all of which take optional parameters
     * from up to 3 groups (method params, authentication, filters). Instead of
     * implementing the interface and adding countless stubs that have basically
     * the same signature, i just map its methods here and use __call().
     */
    private function mapApiMethods(){
        $reflectionClass = new ReflectionClass(SomeApiInterface::class);

        foreach($reflectionClass->getMethods() as $m){
            $this->methodMap[] = $m->name;
        }
    }

    /**
     * Thanks to the PHP 5.6+ "..." token, there's no hassle with the arguments anymore
     * (ugh, bad pun). Just hand the method parameters into the endpoint handler,
     * along with other mandatory params - type hints are your friends.
     *
     * It's magic!
     *
     * @param string $method
     * @param array  $arguments
     *
     * @return \SomeEndpointHandler
     * @throws \Exception
     */
    public function __call($method, $arguments){

        if(in_array($method, $this->methodMap)){
            return new SomeEndpointHandler($this->httpClient, $method, ...$arguments);
        }

        throw new Exception('Endpoint "'.$method.'" does not exist');
    }

}
danillo dot paiva dot toledo at gmail dot com 16-May-2013 07:39
While I was studying Ruby I saw as such interesting things as properties created + its getters and setters in just one line.

I tryied to do the same in PHP and this is the code I have

class Father {
    public function __call($name, $args) {
        if(isset($this->$name)) {
            if(isset($args[0]))
                return $this->$name = $args[0];
            return $this->$name;
        }
        return false;
    }
}

class Child extends Father {
    public $country = "Brazil";
    public $state = "Sao Paulo";
}

Sometimes we don't need things like that on all classes but is quite interesting.
staff at pro-unreal dot de 16-May-2013 06:08
To avoid instanciating the parent instead of the inherited class for __set_state() as reported by jsnell, you could use late static binding introduced in PHP 5.3:

<?php
class A {
    public static function __set_state($data) {
        return new static();
    }
}

class B extends A {
}

$instance = new B();
eval('$test = ' . var_export($instance, true) . ';');
var_dump($test);
// -> object(B)#2 (0) {
// }
?>
igorbt 18-Apr-2013 08:30
In recent versions of PHP, if you define __toString with arguments it will trigger a Fatal error: "__tostring() cannot take arguments". But, if you really need this (like I needed, because my framework heavily used these arguments), you have a workaround:
<?php
class a
{
    public function __toString() {
        list($a) = func_get_args();
        return $a;
    }
}

$a = new a();
echo $a->__toString('PHP'); // PHP
?>
qfox at ya dot ru 06-Sep-2012 12:12
For those of you who have the same trouble as osbertv.
<?php
// ...

$a = new A();
$b = new B();
$a();
$b();
$b->a();

?>

PHP Fatal error:  Call to undefined method B::a()

It's because PHP have bug in parsing syntax (a lot of).
Just make it easier to parse and it would work.
For example, like this:
<?php
$c = $b->a;
$c();
?>

Or this, if you use 5.4 (if you using 5.3 just move call function to the each class which need it or to some base abstract class):
<?php
trait TInnerClosuresInvoker {
  function __call($method, $args) {
    if (isset($this->$method) && is_callable($method)) {
      $closure = $this->$method;
      call_user_func_array($closure, $args);
    } else {
      trigger_error('Call to undefined method '.__CLASS__.'::'.$method.'()', E_USER_ERROR);
    }
  }
}
class A {
  use TInnerClosuresInvoker;
  ...
}
?>

It's a little bit dirty, but it works.
Voitcus at wp dot pl 15-Feb-2012 09:48
You don't need to serialize the class default values, only those which have changed. It might be important for large objects. Note the example below, for simplicity, always serializes arrays and objects.

<?php
class MyBaseClass {
  public $name='object'; // these are default class values
  public $test=1;
  public $test2; // equals to NULL in fact

  public function __construct(){
    $this->test2='some text';  // this is not a default value, although called in the constructor
  }

  public function __sleep(){
    // default class values:
    $defaults=get_class_vars(get_class($this)); // not __CLASS__ or self::, if you'd like to use in descendant classes
    // values of $this object:
    $present=get_object_vars($this);
    $result=array(); // output array
    foreach($present as $key=>$value){
      if(!is_resource($defaults[$key]) && ( // don't store resources
        is_object($defaults[$key]) ||    // always store objects
        is_array($defaults[$key])  ||    // and arrays
          $defaults[$key]!==$value) // and of course all that is not the default value
        ) // tip: try is_scalar as well
      $result[]=$key;
      }
      return $result;
  }
}

$obj1=new MyBaseClass();
echo ($s1=serialize($obj1))."<br>"; // only test2 is stored, as it was changed in the constructor

$obj2=new MyBaseClass();
$obj2->name='object 2'; // change default value here
echo ($s2=serialize($obj2))."<br>"; // stored name and test2

$obj3=new MyBaseClass();
$obj3->test2=NULL; // switch back to default value
echo ($s3=serialize($obj3))."<br>"; // nothing is stored but the class name

// let us check if we can retrieve the objects
unset($obj1, $obj2, $obj3);
$obj1=unserialize($s1);
$obj2=unserialize($s2);
$obj3=unserialize($s3);
var_dump($obj1);
var_dump($obj2);
var_dump($obj3);
?>
daan dot broekhof at gmail dot com 14-Feb-2012 10:54
Ever wondered why you can't throw exceptions from __toString()? Yeah me too.

Well now you can! This trick allows you to throw any type of exception from within a __toString(), with a full & correct backtrace.

How does it work? Well PHP __toString() handling is not as strict in every case: throwing an Exception from __toString() triggers a fatal E_ERROR, but returning a non-string value from a __toString() triggers a non-fatal E_RECOVERABLE_ERROR.
Add a little bookkeeping, and can circumvented this PHP deficiency!
(tested to work PHP 5.3+)

<?php

set_error_handler(array('My_ToStringFixer', 'errorHandler'));
error_reporting(E_ALL | E_STRICT);

class My_ToStringFixer
{
    protected static $_toStringException;

    public static function errorHandler($errorNumber, $errorMessage, $errorFile, $errorLine)
    {
        if (isset(self::$_toStringException))
        {
            $exception = self::$_toStringException;
            // Always unset '_toStringException', we don't want a straggler to be found later if something came between the setting and the error
            self::$_toStringException = null;
            if (preg_match('~^Method .*::__toString\(\) must return a string value$~', $errorMessage))
                throw $exception;
        }
        return false;
    }
   
    public static function throwToStringException($exception)
    {
        // Should not occur with prescribed usage, but in case of recursion: clean out exception, return a valid string, and weep
        if (isset(self::$_toStringException))
        {
            self::$_toStringException = null;
            return '';
        }

        self::$_toStringException = $exception;

        return null;
    }
}

class My_Class
{
    public function doComplexStuff()
    {
        throw new Exception('Oh noes!');
    }

    public function __toString()
    {
        try
        {
            // do your complex thing which might trigger an exception
            return $this->doComplexStuff();
        }
        catch (Exception $e)
        {
            // The 'return' is required to trigger the trick
            return My_ToStringFixer::throwToStringException($e);
        }
    }
}

$x = new My_Class();

try
{
    echo $x;
}
catch (Exception $e)
{
    echo 'Caught Exception! : '. $e;
}
?>
osbertv at yahoo dot com 29-Dec-2011 09:42
Invoking a class inside a class results in an error.

<?php
class A
{
    public function __invoke()
    {
        echo "Invoking A() Class";
    }
}

class B
{
    public $a;
   
    public function __construct()
    {
        $this->a = new A();
    }
   
    public function __invoke()
    {
        echo "Invoking B() Class";
    }
}

$a = new A();
$b = new B();
$a();
$b();
$b->a();

?>

returns
Invoking B() Class
PHP Fatal error:  Call to undefined method B::a()
hyponiq at gmail dot com 26-Sep-2011 06:07
I think it's fair to note the undocumented fact that the __invoke magic method can take any number of arguments (or none).

Example:
<?php
class InvokeNoParams {
    function __invoke()
    {
        print __METHOD__ . PHP_EOL;
        $i = 1;
        foreach (func_get_args() as $arg) {
            print "The value of \$param{$i} is: " . $arg . PHP_EOL;
            ++$i;
        }
        print PHP_EOL;
    }
}
 
class InvokeSingleParam {
    function __invoke($param1)
    {
        print __METHOD__ . PHP_EOL;
        print "Value of \$param1 is: " . $param1 . PHP_EOL . PHP_EOL;
    }
}
 
class InvokeMultiParams {
    function __invoke($param1, $param2, $param3) {
        print __METHOD__ . PHP_EOL;
        print "Value of \$param1 is: " . $param1 . PHP_EOL;
        print "Value of \$param2 is: " . $param2 . PHP_EOL;
        print "Value of \$param3 is: " . $param3 . PHP_EOL . PHP_EOL;
    }
}
 
$no = new InvokeNoParams;
$single = new InvokeSingleParam;
$multi = new InvokeMultiParams;
 
$no(1, 2, 3);
$single('one param');
$multi('param 1', 'param 2', 'param 3');
?>

This outputs:
InvokeNoParams::__invoke
The value of $param1 is: 1
The value of $param2 is: 2
The value of $param3 is: 3

InvokeSingleParam::__invoke
Value of $param1 is: one param

InvokeMultiParams::__invoke
Value of $param1 is: param 1
Value of $param2 is: param 2
Value of $param3 is: param 3
Wesley 25-May-2011 12:10
Warning __toString can be triggerd more then one time

<?php
if(strstr(substr($obj,0,1024), 'somestuff')
    echo $obj;
return 'missing somestuff at the start, create container!';

substr() will trigger a __toString aswell as echo $obj;
?>

wich cause a performance issue since it will gather all data twice.

what i used as a hotfix:

<?php
__toString(){
  if(null === $this->sToString)
     $this->sToString = $this->_show();
  return $this->sToString;
}
?>
Anonymous 24-Jul-2010 07:41
Concerning __set() with protected/private/overloaded properties, the behavior might not be so intuitive without knowing some underlying rules.  Consider this test object for the following examples...

<?php
class A {
    protected $test_int = 2;
    protected $test_array = array('key' => 'test');
    protected $test_obj;
   
    function __construct() {
        $this->test_obj = new stdClass();
        }
       
    function __get($prop) {
        return $this->$prop;
        }
       
    function __set($prop, $val) {
        $this->$prop = $val;
        }
    }

$a = new A();

?>

Combined Operators (.=, +=, *=, etc): you must also define a companion __get() method to grant write -and- read access to the property.  Remember, "$x += $y" is shorthand for "$x = $x + $y".  In other words, "__set($x, (__get($x) + $y))".

Properties that are Arrays: attempting to set array values like "$a->test_array[] = 'asdf';" from outside this object will result in an "Indirect modification of overloaded property" notice and the operation completely ignored.  You can't use '[]' for array value assignment in this context (with the exception only if you made __get() return by reference, in which case, it would work fine and bypass the __set() method altogether).  You can work around this doing something like unioning the array instead:

<?php

$a->test_array[] = 'asdf'; // notice given and ignored unless __get() was declared to return by reference
$a->test_array += array(1 => 'asdf'); // to add a key/value
$a->test_array = array("key" => 'asdf') + $a->test_array; // to overwrite a  key/value.

?>

Properties that are Objects: as long as you have that __get() method, you can freely access and alter that sub object's own properties, bypassing __set() entirely.  Remember, objects are assigned and passed by reference naturally.

<?php

$a->test_obj->prop = 1; // fine if $a did not have a set method declared.

?>

All above tested in 5.3.2.
tom 18-Jul-2010 03:20
Note a common pitfall when using __wakeup.

If you unserialize a datastructure, you may not rely on the parent object to have been fully unserialized by the time __wakeup is called. Example

<?php
class A {
 public $b;
 public $name;
}

class B extends A {
 public $parent;
 public function __wakeup() {
  var_dump($parent->name);
 }
}

$a = new A();
$a->name = "foo";
$a->b = new B();
$a->b->parent = $a;
$s = serialize($a);
$a = unserialize($s);
?>

Expected output: "foo".
Actual output: NULL.

Reason: $b is unserialized before $name. By the time B::__wakeup is called, $a->name does not yet have a value.

So be aware that the order in which your class variables are defined is important! You need to manually order them by dependencies - or write a __sleep function and order them by depencies there. (Currently I can't tell which option I hate more)
Anonymous 30-Jun-2010 09:29
C++-style operator overloading finally makes an appearance with the introduction to __invoke().  Unfortunately, with just '()'.  In that sense, it is no more useful than having a default class method (probably quite useful actually) and not having to type out an entire method name.  Complimenting wbcarts at juno dot com's point class below, the following allows calculating distance between one or more graph points...

<?php

class point {
    public $x;
    public $y;

    function __construct($x=0, $y=0) {
        $this->x = (int) $x;
        $this->y = (int) $y;
        }
       
    function __invoke() {
        $args = func_get_args();
        $total_distance = 0;
        $current_loc = $this;
        foreach ($args as $arg) {
            if (is_object($arg) and (get_class($arg) === get_class($this))) {
                $total_distance += sqrt(pow($arg->x - $current_loc->x, 2) + pow((int) $arg->y - $current_loc->y, 2));
                $current_loc = $arg;
                }
            else {
                trigger_error("Arguments must be objects of this class.");
                return;
                }
            }
        return $total_distance;
        }
   
    }

$p1 = new point(1,1);
$p2 = new point(23,-6);
$p3 = new point(15,20);
echo $p1($p2,$p3,$p1); // round trip 73.89

?>

Functionally, __invoke() can also be used to mimic the use of variable functions.  Sadly, attempting any calling of __invoke() on a static level will produce a fatal error.
moechofe 25-Jul-2009 02:47
__invoke() cannot be used to create fluente interface like in the "D language"

<?php
class CallableClass
{
    var $next;
    function __invoke($x)
    {
        var_dump($x);
        return $this;
   }
}
$obj = new CallableClass;
$obj->next = new CallableClass;
var_dump( $obj(5) ); // OK!
var_dump( $obj(5)(6) ); // Parse error
var_dump( $obj->next(7) ); // Fatal error: Call to undefined method CallableClass::next()
var_dump( {$obj->next}(7) ); // Parse error
?>
zach at bygeekz dot com 25-May-2009 12:45
Try this one on.

<?php
$ret = new Test(true);
var_dump((bool)(string)$ret);
var_dump($ret);
$ret=null;
$ret = new Test();
var_dump((bool)(string)$ret);
var_dump($ret);

class Test {
    protected $state=null;
    function __construct($state=null) {
        $this->state = $state;
    }
    function __toString() {
        if ($this->state) { return "1"; } else { return "0"; }
    }
}
?>

You could for instance do..

if(!(bool)(string)$ret) { do_something!; }

Alternatively, just make state public, and check it.

if(!$ret->state) {}.

There is no automatic way I have found aside from some internal state check to verify a class. It will always return an object. The only way around that is to force it out to string either where I did, or $ret = (string) new Test(); then test the bool of your output..

if (!$ret) { echo "noooo!"; }

But now you have no calling methods, so I hope you passed some data in to get a usable string out.

Of course, if your class isn't named test, you can add a method..

public function test() {
     return $this->state;
}

Logically that will work regardless of the _toString(), but I had hoped to post this to help others see that there are a multitude of ways to check the validity of a class once it is loaded. In __construct you can add any number of checks and set your state appropriately.
rudie-de-hotblocks at osu1 dot php dot net 09-Apr-2009 06:35
Note also that the constructor is executed also, and before __set_state(), making this magic function less magic, imho, (except for the ability to assign private members).
muratyaman at gmail dot com 07-Jan-2009 07:54
Regarding __toString:

<?php
class my_tag_A{

    public $id='';
    public $href='';
    public $target='';
    public $class='';
   
    public $label='';
   
    function __construct($href, $label){
        $this->href = $href;
        $this->label = $label;
    }
   
    public function __toString(){
        return '<a '.$this->nz_arr(array('id', 'href', 'target', 'class')). ' >' . $this->label . '</a>';
    }
   
    function nz_arr($attrib_arr){
        $s = '';
        foreach($attrib_arr as $attrib){
            $s .= $this->nz($attrib);
        }
        return $s;
    }

    /**
     * Print the tag attribute if it is not blank, such as id="$this->id"
     * @param string $attrib
     * @return string
     */
    function nz($attrib){
        $s = '';
        if($this->$attrib != '') $s = $attrib .' = "' . $this->$attrib . '"';
        return $s;
    }

    //This causes RECURSION because of parsing between double quotes. This is a very UNEXPECTED behaviour!
    function nz_($attrib){
        $s = '';
        if($this->$attrib != '') $s = "$attrib = \"$this->$attrib\"";
        return $s;
    }
   
}//end  class

//usage
$a = new my_tag_A('abc.php', 'ABC'); $a->target = '_blank';
echo $a;
//prints:
//    <a href="abc.php" target="_blank" >ABC</a>
?>
jsnell at e-normous dot com 03-Dec-2008 02:01
Be very careful to define __set_state() in classes which inherit from a parent using it, as the static __set_state() call will be called for any children.  If you are not careful, you will end up with an object of the wrong type.  Here is an example:

<?php
class A
{
    public $var1;

    public static function __set_state($an_array)
    {
        $obj = new A;
        $obj->var1 = $an_array['var1']; 
        return $obj;
    }
}

class B extends A {
}

$b = new B;
$b->var1 = 5;

eval('$new_b = ' . var_export($b, true) . ';');
var_dump($new_b);
/*
object(A)#2 (1) {
  ["var1"]=>
  int(5)
}
*/
?>
patricknegri at gmail dot com 26-Oct-2008 03:57
Imports Pattern - Extend Classes in Real Time:

<?php
class BaseClass
{
    var $__imported;
    var $__imported_functions;
   
    function __construct()
    {
        $__imported = Array();
        $__imported_functions = Array();
    }
   
    function Imports($object)
    {
        $new_imports = new $object();
        $imports_name = get_class($new_imports);
        array_push( $__imported, Array($imports_name,$new_imports) );
        $imports_function = get_class_methods($new_imports);
        foreach ($imports_function as $i=>$function_name)
        {
            $this->__imported_functions[$function_name] = &$new_imports;
        }       
    }
   
    function __call($m, $a)
    {   
        if (array_key_exists($m,$this->__imported_functions))
        {                   
            return call_user_func_array(Array($this->__imported_functions[$m],$m),$a);
        }
        throw new ErrorException ('Call to Undefined Method/Class Function', 0, E_ERROR);
    }
}

class ExternalFunc
{
    function TestB()
    {
        echo "External Imported!";
    }
}

class B extends BaseClass
{
    function __construct()
    {
        $this->Imports("ExternalFunc");
    }
   
    function Msg()
    {
        echo "Hello world<br />";
    }
}

$b = new B();
$b->Msg();
// or call $b->Imports("ExternalFunc");
$b->TestB();
//$b->TestB(1,3,4);
?>
jon at webignition dot net 03-Oct-2008 07:26
The __toString() method is extremely useful for converting class attribute names and values into common string representations of data (of which there are many choices). I mention this as previous references to __toString() refer only to debugging uses.

I have previously used the __toString() method in the following ways:

 - representing a data-holding object as:
   - XML
   - raw POST data
   - a GET query string
   - header name:value pairs

 - representing a custom mail object as an actual email (headers then body, all correctly represented)

When creating a class, consider what possible standard string representations are available and, of those, which would be the most relevant with respect to the purpose of the class.

Being able to represent data-holding objects in standardised string forms makes it much easier for your internal representations of data to be shared in an interoperable way with other applications.
wbcarts at juno dot com 02-Oct-2008 04:12
To be helpful, the __toString() method should return the class name and the state of all its properties inside square brackets.

<?php
class Point {
  protected $x, $y;

  public function __construct($xVal = 0, $yVal = 0) {
    $this->x = $xVal;
    $this->y = $yVal;
  }   

  public function __toString() {      // the function we're interested in...
    return "Point[x=$this->x, y=$this->y]";
  }
}

$point1 = new Point(10, 10);
$point2 = new Point(50, 50);
echo $point1 . '<br>';
echo $point2 . '<br><br>';
?>

Point[x=10, y=10]
Point[x=50, y=50]

Classes that include objects, should call that objects __toString() method.

<?php
class Line {
  protected $start, $end;

  public function __construct(Point $p1, Point $p2){
    $this->start = $p1;
    $this->end = $p2;
  }

  public function __toString() {      // the function we're interested in...
    return 'Line[start=' . $this->start->__toString() .  // call __toString()
     ', end=' . $this->end->__toString() . ']';          // call __toString()
  }
}

echo (new Line($point1, $point2));
?>

Line[start=Point[x=10, y=10], end=Point[x=50, y=50]]
rc @ nospam @ vorklift dot sea oh em 07-Aug-2008 07:03
A note: __wakeup occurs before saving the unserialization of an session object.

Therefore, $_SESSION['var']::__wakeup() setting $_SESSION['var'] = new Class() will fail and $_SESSION['var'] will remain unchanged.

This means that if you have a pseudo-temporary object that contains a class to auto revert to, you have to revert that session object in the initialization of the website rather than via a __wakeup() script.
Anonymous 31-May-2008 04:24
Serializing objects is problematic with references. This is solved redefining the __sleep() magic method. This is also problematic when parent class has private variables since the parent object is not accessible nor its private variables from within the child object.

I found a solution that seems working for classes that implements this __sleep() method, and for its subclasses. Without more work in subclasses. The inheritance system does the trick.

Recursively __sleep() call parent' __sleep() and return the whole array of variables of the object instance to be serialized.

<?php
class foo {
}

class a {
  private $var1;

  function __construct(foo &$obj = NULL) {
    $this->var1 = &$obj;
  }

  /** Return its variables array, if its parent exists and the __sleep method is accessible, call it and push the result into the array and return the whole thing. */
  public function __sleep() {
    $a = array_keys(get_object_vars(&$this));
    if (method_exists(parent, '__sleep')) {
      $p = parent::__sleep();
      array_push($a, $p);
    };
    return $a;
  }
}

class b extends a {
  function __construct(foo &$obj = NULL) {
    parent::__construct($obj);
  }
}

session_start();
$myfoo = &new foo();
$myb = &new b($myfoo);
$myb = unserialize(serialize(&$myb));
?>

This should work, I haven't tested deeper.
yanleech at gmail dot com 10-May-2008 06:24
Maybe we can using unserialize() & __wakeup() instead "new" when creating a new instance of class.

Consider following codes:

class foo
{
    static public $WAKEUP_STR = 'O:3:"foo":0:{}';
    public function foo(){}
    public function bar(){}
}

$foo = unserialize(foo::$WAKEUP_STR);
michal dot kocarek at seznam dot cz 18-Apr-2008 02:34
Remember that setters and getters (__set, __get) will work in your class as long as you NOT SET the property with given name.

If you still want to have the public property definition in the class source code (phpDocumentor, editor code completition, or any other reason) when using these magic methods, simply unset() your public properties inside the constructor.
__set/__get function will be called and code reader will see at first sight, which public properties are available.

Example:
<?php
class user {
   /**
    * @var int Gets and sets the user ID
    */
   public $UserID;
   private $_userID;

   public function __construct() {

      // All the magic is in single line:
      // We unset public property, so our setters and getters
      // are used and phpDoc and editors with code completition are happy
      unset($this->UserID);

   }

   public function __set($key, $value) {
      // assign value for key UserID to _userID property
   }

   public function __get($key) {
      // return value of _userID for UserID property
   }
}
?>
dhuseby domain getback tld com 29-Feb-2008 06:22
The above hint for using array_keys((array)$obj) got me investigating how to get __sleep to really work with object hierarchies.

With PHP 5.2.3, If you want to serialize an object that is part of an object hierarchy and you want to selectively serialize members (public, private, and protected) by manually specifying the array of members, there are a few simple rules for naming members that you must follow:

1. public members should be named using just their member name, like so:

<?php
class Foo {
    public $bar;

    public function __sleep() {
        return array("bar");
    }
}
?>

2. protected members should be named using "\0" . "*" . "\0" . member name, like so:

<?php
class Foo {
    protected $bar;

    public function __sleep() {
        return array("\0*\0bar");
    }
}
?>

3. private members should be named using "\0" . class name . "\0" . member name, like so:

<?php
class Foo {
    private $bar;

    public function __sleep() {
        return array("\0Foo\0bar");
    }
}
?>

So with this information let us serialize a class hierarchy correctly:

<?php

class Base {
    private $foo = "foo_value";
    protected $bar = "bar_value";

    public function __sleep() {
        return array("\0Base\0foo", "\0*\0bar");
    }
}

class Derived extends Base {
    public $baz = "baz_value";
    private $boo = "boo_value";

    public function __sleep() {
        // we have to merge our members with our parent's
        return array_merge(array("baz", "\0Derived\0boo"), parent::__sleep());
    }
}

class Leaf extends Derived {
    private $qux = "qux_value";
    protected $zaz = "zaz_value";
    public $blah = "blah_value";

    public function __sleep() {
        // again, merge our members with our parent's
        return array_merge(array("\0Leaf\0qux", "\0*\0zaz", "blah"), parent::__sleep());
    }
}

// test it
$test = new Leaf();
$s = serialize($test);
$test2 = unserialize($s);
echo $s;
print_r($test);
print_r($test2);

?>

Now if you comment out all of the __sleep() functions and output the serialized string, you will see that the output doesn't change.  The most important part of course is that with the proper __sleep() functions, we can unserialize the string and get a properly set up object.

I hope this solves the mystery for everybody.  __sleep() does work, if you use it correctly :-)
andrew dot minerd at sellingsource dot com 08-Nov-2007 07:55
Until __sleep is "fixed" (here's hoping), a function that will return ALL members of a given object -- public, protected, AND private:

<?php
        public function getPropertyNames(array $filter = NULL)
        {
            $rc = new ReflectionObject($this);
            $names = array();

            while ($rc instanceof ReflectionClass)
            {
                foreach ($rc->getProperties() as $prop)
                {
                    if (!$filter || !in_array($prop->getName(), $filter))
                        $names[] = $prop->getName();
                }

                $rc = $rc->getParentClass();
            }

            return $names;
        }
?>
amir_abiri at ipcmedia dot com 24-Jul-2007 04:58
Another small thing that is important to note about __sleep() and privte member variables:

<?php
class A
{
  private $a;
 
  public function __construct()
  {
    $this->a = 1;
  }
}

class B extends A
{
  protected $b;
 
  public function __construct()
  {
    parent::__construct();
    $this->b = 2;
  }
 
  function __sleep()
  {
    return array('a', 'b');
  }
}

serialize(new B);
?>

result:
Notice: serialize(): "a" returned as member variable from __sleep() but does not exist in ...

To summerize: in a given class hierarchy in which parent classes contain private member variables, those variables are serialized when __sleep() is not defined. However, once __sleep() is defined, there is no way to make those private member variables serialized as well. From that point on, serialization is performed from the visibility scope of the subclass.

It is particularly important to note this little quirk when designing base classes that their derivables may be serialized, or when subclassing an external library class.
alejandro dot gama at gmail dot com 09-May-2007 07:47
Referering my previus note: there was an error in the code. But i find a better way:

<?
session_start();

class Classes{
  private $name;
  private $statics;
   
  function __construct($name){
    $this->name=$name;
    $this->statics=array();
  }
   
  function setStatic($k,$v){
    if(!is_resource($v))
      $this->statics[$k]=$v;
  }
   
   
  function __wakeup(){
    foreach($this->statics as $k=>$v)
      eval($this->name."::\$".$k."=\$this->statics['".$k."'];");
  }
}

function storeStaticAttributes(){
  $classes=get_declared_classes();
  foreach($classes as $name){
    $reflect=new ReflectionClass($name);

    if($reflect->isUserDefined()){
      $statics=$reflect->getStaticProperties();

      if(empty($_SESSION["_classes"]))
        $_SESSION["_classes"]=array();
           
      if(empty($_SESSION["_classes"][$name]))
        $_SESSION["_classes"][$name]=new Classes($name);

      foreach($statics as $k=>$v)
        $_SESSION["_classes"][$name]->setStatic($k,$v);   
    }
  }
}
register_shutdown_function('storeStaticAttributes');
?>
Travis Swicegood 08-May-2007 07:43
There is no need to use eval() to mimic mixins (i.e., multiple inheritance) within PHP 5.  You only need to:

<?php

class MyClass
{
    private $_obj = null;
    public function __construct($obj)
    {
        $this->_obj = $obj;
    }

    public function __call($method, $args)
    {
        if (!method_exists($this->_obj, $method)) {
            throw new Exception("unknown method [$method]");
        }

        return call_user_func_array(
            array($this->_obj, $method),
            $args
        );
    }
}

?>

You could just as easily add an addMixin() method that would allow you to add multiple objects to an array, and then iterate over that array until you found the right method.  As noted, these are referred to as a Mixins in other languages.
adar at darkpoetry dot de 04-May-2007 06:09
Maybe not really new and all in all definitely not the best solution,but if you cant extend a class (if your class alreay extends an abstract or other things like that) you can 'fake' a extend.

<?php
class MyClass
        extends SomeAbstractUnknownClass {

    private $classObject;

    public function __construct ( classObject $classToExtend ) {
        $this->classObject = $classToExtend;
    }

    public function __call($func, $var) {
        if ( !count($var) ) {
            return $this->classObject->$func($var);
        } else {
            $str = '';
            $values = array_values($var);
            for ( $i=0; $i<count($values); $i++ ) {
                $str .= "'".$values[$i]."' ,";
            }  
            $str = substr($str, 0, -2);
            return eval('return $this->classObject->'.$func.'('.$str.');');
        }  
    }  
}
?>

So if you'll do a $myClass->unknownMethod() and it is found neither in MyClass nor in SomeAbstractUnknownClass, MyClass will try to call this method in $classObject.

I use this for 'extending' a UserObject-Class which already extends an other one.

Better solutions are always welcome ;)
Dérico Filho 23-Jan-2007 07:33
Since PHP 5.2.0, you'll always get an error like this:
"Object of class foo could not be converted to string"

When one tries to use an object as string, for instance:

class Test{}
echo new Test();

Thus, one way to avoid this problem is to programme the magic method __toString.

However, in the older versions, it would output a string saying that it was an object together a unique obj id. Therefore, the __toString() method must comply with this behaviour.

My suggestion:

class Test{
    function __toString(){
        if(!isset($this->__uniqid))
            $this->__uniqid = md5(uniqid(rand(), true));
        return(get_class($this)."@".$this->__uniqid);
    }

}

echo new Test();

would output something like this:

Test@6006ba04f5569544c10a588b04849cf7
jstubbs at work-at dot co dot jp 02-Sep-2006 12:32
$myclass->foo['bar'] = 'baz';

When overriding __get and __set, the above code can work (as expected) but it depends on your __get implementation rather than your __set. In fact, __set is never called with the above code. It appears that PHP (at least as of 5.1) uses a reference to whatever was returned by __get. To be more verbose, the above code is essentially identical to:

$tmp_array = &$myclass->foo;
$tmp_array['bar'] = 'baz';
unset($tmp_array);

Therefore, the above won't do anything if your __get implementation resembles this:

function __get($name) {
    return array_key_exists($name, $this->values)
        ? $this->values[$name] : null;
}

You will actually need to set the value in __get and return that, as in the following code:

function __get($name) {
    if (!array_key_exists($name, $this->values))
        $this->values[$name] = null;
    return $this->values[$name];
}
taylorbarstow at google's mail service 15-May-2006 01:54
I've just come accross something interesting relating to storing PHP5 objects in a session.  If you don't provide an __autoload(), then you MUST load the class definition before calling session_start().  I guess that when you call session_start(), any objects in the session are unserialized then and there and placed into $_SESSION.  If you don't provide the class definition before calling session_start(), your object will get the class __PHP_Incomplete_Class, and you won't be able to use it for anything.

Examples:

<?php
session_start();
require_once 'MyClass.php';
$obj = new MyClass;
$_SESSION['obj'] = $obj;
?>

Works fine.  Then on a subsequent page load:

<?php
session_start();
require_once 'MyClass.php';
$_SESSION['obj']->callSomeMethod();
?>

Fatal error:  The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "MyClass" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition.

But if you do this instead, it works fine:

<?php
require_once 'MyClass.php';
session_start();
$_SESSION['obj']->callSomeMethod();
?>

Hopefully in some future release of PHP, __PHP_Incomplete_Class will be smart enough to check for a class definition at time of use (method call or property operation), and, if the class exists, magically "complete" itself and turn into the desired object.
rayRO 02-Apr-2006 09:55
If you use the Magical Method '__set()', be shure that the call of
<?php
$myobject->test['myarray'] = 'data';
?>
will not appear!

For that u have to do it the fine way if you want to use __set Method ;)
<?php
$myobject->test = array('myarray' => 'data');
?>

If a Variable is already set, the __set Magic Method already wont appear!

My first solution was to use a Caller Class.
With that, i ever knew which Module i currently use!
But who needs it... :]
There are quiet better solutions for this...
Here's the Code:

<?php
class Caller {
    public $caller;
    public $module;

    function __call($funcname, $args = array()) {
        $this->setModuleInformation();

        if (is_object($this->caller) && function_exists('call_user_func_array'))
            $return = call_user_func_array(array(&$this->caller, $funcname), $args);
        else
            trigger_error("Call to Function with call_user_func_array failed", E_USER_ERROR);
       
        $this->unsetModuleInformation();
        return $return;
    }

    function __construct($callerClassName = false, $callerModuleName = 'Webboard') {
        if ($callerClassName == false)
            trigger_error('No Classname', E_USER_ERROR);

        $this->module = $callerModuleName;

        if (class_exists($callerClassName))
            $this->caller = new $callerClassName();
        else
            trigger_error('Class not exists: \''.$callerClassName.'\'', E_USER_ERROR);

        if (is_object($this->caller))
        {
            $this->setModuleInformation();
            if (method_exists($this->caller, '__init'))
                $this->caller->__init();
            $this->unsetModuleInformation();
        }
        else
            trigger_error('Caller is no object!', E_USER_ERROR);
    }

    function __destruct() {
        $this->setModuleInformation();
        if (method_exists($this->caller, '__deinit'))
            $this->caller->__deinit();
        $this->unsetModuleInformation();
    }

    function __isset($isset) {
        $this->setModuleInformation();
        if (is_object($this->caller))
            $return = isset($this->caller->{$isset});
        else
            trigger_error('Caller is no object!', E_USER_ERROR);
        $this->unsetModuleInformation();
        return $return;
    }

    function __unset($unset) {
        $this->setModuleInformation();
        if (is_object($this->caller)) {
            if (isset($this->caller->{$unset}))
                unset($this->caller->{$unset});
        }
        else
            trigger_error('Caller is no object!', E_USER_ERROR);
        $this->unsetModuleInformation();
    }

    function __set($set, $val) {
        $this->setModuleInformation();
        if (is_object($this->caller))
            $this->caller->{$set} = $val;
        else
            trigger_error('Caller is no object!', E_USER_ERROR);
        $this->unsetModuleInformation();
    }

    function __get($get) {
        $this->setModuleInformation();
        if (is_object($this->caller)) {
            if (isset($this->caller->{$get}))
                $return = $this->caller->{$get};
            else
                $return = false;
        }
        else
            trigger_error('Caller is no object!', E_USER_ERROR);
        $this->unsetModuleInformation();
        return $return;
    }
   
    function setModuleInformation() {
        $this->caller->module = $this->module;
    }

    function unsetModuleInformation() {
        $this->caller->module = NULL;
    }
}

// Well this can be a Config Class?
class Config {
    public $module;

    public $test;

    function __construct()
    {
        print('Constructor will have no Module Information... Use __init() instead!<br />');
        print('--> '.print_r($this->module, 1).' <--');
        print('<br />');
        print('<br />');
        $this->test = '123';
    }
   
    function __init()
    {
        print('Using of __init()!<br />');
        print('--> '.print_r($this->module, 1).' <--');
        print('<br />');
        print('<br />');
    }
   
    function testFunction($test = false)
    {
        if ($test != false)
            $this->test = $test;
    }
}

echo('<pre>');
$wow = new Caller('Config', 'Guestbook');
print_r($wow->test);
print('<br />');
print('<br />');
$wow->test = '456';
print_r($wow->test);
print('<br />');
print('<br />');
$wow->testFunction('789');
print_r($wow->test);
print('<br />');
print('<br />');
print_r($wow->module);
echo('</pre>');
?>

Outputs something Like:

Constructor will have no Module Information... Use __init() instead!
-->  <--

Using of __init()!
--> Guestbook <--

123

456

789

Guestbook
ksamvel at gmail dot com 10-Feb-2006 09:29
To copy base part of derived class appropriate method in base should be defined. E.g.:

  class A {
    public function setAVar( $oAVar) { $this->oAVar = $oAVar; }
    public function getAVar() { return $this->oAVar; }

    public function copyA( &$roDest) {
      if( $roDest instanceof A)
        $this->oAVar = $roDest->oAVar;
    }

    private $oAVar;
  }

  class B extends A {
    public function setBVar( $oBVar) { $this->oBVar = $oBVar; }
    public function getBVar() { return $this->oBVar; }

    private $oBVar;
  }

  $oA = new A();
  $oB = new B();

  $oA->setAVar( 4);

  $oB->setAVar( 5);
  $oB->setBVar( 6);
  echo "oA::oAVar " . $oA->getAVar() . "<br>";
  echo "oB::oAVar " . $oB->getAVar() . "<br>";
  echo "oB::oBVar " . $oB->getBVar() . "<br>";
  echo "<br>";

  $oB->copyA( $oA);

  echo "oA::oAVar " . $oA->getAVar() . "<br>";
  echo "oB::oAVar " . $oB->getAVar() . "<br>";
  echo "oB::oBVar " . $oB->getBVar() . "<br>";

Output:

oA::oAVar 4
oB::oAVar 5
oB::oBVar 6

oA::oAVar 4
oB::oAVar 4
oB::oBVar 6
b dot schoppmeier at bas-consult dot de 26-Jan-2006 03:18
The sequence of events regarding __sleep and __destruct is unusual __ as __destruct is called before __sleep. The following code snippet:

<?php
$sequence = 0;
class foo {
    public $stuff;   
    public function __construct($param) {
        global $sequence;
        echo "Seq: ", $sequence++, " - constructor\n";
        $this->stuff = $param;
    }
    public function __destruct() {
        global $sequence;
        echo "Seq: ", $sequence++, " - destructor\n";
    }
    public function __sleep() {
        global $sequence;
        echo "Seq: ", $sequence++, " - __sleep\n";
        return array("stuff");
    }
    public function __wakeup() {
        global $sequence;
        echo "Seq: ", $sequence++, " - __wakeup\n";
    }
}
session_start();
$_SESSION["obj"] = new foo("A foo");
?>

yields the output:

Seq: 0 - constructor
Seq: 1 - destructor
Seq: 2 - __sleep

Only when you end your script with a call to session_write_close() as in:

<?php
$sequence = 0;
class foo {
    public $stuff;   
    public function __construct($param) {
        global $sequence;
        echo "Seq: ", $sequence++, " - constructor\n";
        $this->stuff = $param;
    }
    public function __destruct() {
        global $sequence;
        echo "Seq: ", $sequence++, " - destructor\n";
    }
    public function __sleep() {
        global $sequence;
        echo "Seq: ", $sequence++, " - __sleep\n";
        return array("stuff");
    }
    public function __wakeup() {
        global $sequence;
        echo "Seq: ", $sequence++, " - __wakeup\n";
    }
}
session_start();
$_SESSION["obj"] = new foo("A foo");
session_write_close();
?>

the sequence is as common sense would expect it to be as the following output shows:

Seq: 0 - constructor
Seq: 1 - __sleep
Seq: 2 - destructor
docey 09-Dec-2005 08:44
about __sleep and _wakeup, consider using a method like this:

class core
{

 var $sub_core; //ref of subcore
 var $_sleep_subcore; // place where serialize version of sub_core will be stored

 function core(){
  $this->sub_core = new sub_core();
  return true;
 }

 function __wakeup()
 {
  // on wakeup of core, core unserializes sub_core
  // wich it had stored when it was serialized itself
  $this->sub_core = unserialize($this->_sleep_subcore);
  return true;
 }

 function __sleep()
 {
  // sub_core will be serialized when core is serialized.
  // the serialized subcore will be stored as a string inside core.
   $this->_sleep_subcore = serialize($this->sub_core);
   $return_arr[] = "_sleep_subcore";
   return $return_arr;
 }

}

class sub_core
{
 var $info;

 function sub_core()
 {
  $this->info["somedata"] = "somedata overhere"
 }

 function __wakeup()
 {
  return true;
 }

 function __sleep()
 {
  $return_arr[] = "info"
  return $return_arr;
 }

}

this way subcore is being serialized by core when core is being serialized. subcore handles its own data and core stores it as a serialize string inside itself. on wakeup core unserializes subcore.

this may have a performance cost, but if you have many objects connected this way this is the best way of serializing them. you only need to serialize the the main object wich will serialize all those below which will serialize all those below them again. in effect causing a sort of chainreaction in wich each object takes care of its own info.

offcoarse you always need to store the eventualy serialized string in a safe place. somebody got experience with this way of __wakeup and __sleep.

works in PHP4&5
martin dot goldinger at netserver dot ch 15-Aug-2005 04:47
When you use sessions, its very important to keep the sessiondata small, due to low performance with unserialize. Every class shoud extend from this class. The result will be, that no null Values are written to the sessiondata. It will increase performance.

<?
class BaseObject
{
    function __sleep()
    {
        $vars = (array)$this;
        foreach ($vars as $key => $val)
        {
            if (is_null($val))
            {
                unset($vars[$key]);
            }
        }   
        return array_keys($vars);
    }
};
?>
jeffxlevy at gmail dot com 13-Aug-2005 06:26
Intriguing what happens when __sleep() and __wakeup() and sessions() are mixed. I had a hunch that, as session data is serialized, __sleep would be called when an object, or whatever, is stored in _SESSION. true. The same hunch applied when session_start() was called. Would __wakeup() be called? True. Very helpful, specifically as I'm building massive objects (well, lots of simple objects stored in sessions), and need lots of automated tasks (potentially) reloaded at "wakeup" time. (for instance, restarting a database session/connection).
mastabog at hotmail dot com 12-Aug-2005 05:06
In reply to krisj1010 at gmail.com below:

__sleep() handles protected/private properties very well. You should never rely on get_class_vars() to retrieve property names since this function only returns the public properties. Use the Reflection API instead for that purpose. Better yet, if you know which ones you want to save it is always faster to specify the return array manually.
ddavenport at newagedigital dot com 26-Jan-2005 11:09
One of the principles of OOP is encapsulation--the idea that an object should handle its own data and no others'.  Asking base classes to take care of subclasses' data, esp considering that a class can't possibly know how many dozens of ways it will be extended, is irresponsible and dangerous.

Consider the following...

<?php
class SomeStupidStorageClass
{
  public function getContents($pos, $len) { ...stuff... }
}

class CryptedStorageClass extends SomeStupidStorageClass
{
  private $decrypted_block;
  public function getContents($pos, $len) { ...decrypt... }
}
?>

If SomeStupidStorageClass decided to serialize its subclasses' data as well as its own, a portion of what was once an encrypted thingie could be stored, in the clear, wherever the thingie was stored.  Obviously, CryptedStorageClass would never have chosen this...but it had to either know how to serialize its parent class's data without calling parent::_sleep(), or let the base class do what it wanted to.

Considering encapsulation again, no class should have to know how the parent handles its own private data.  And it certainly shouldn't have to worry that users will find a way to break access controls in the name of convenience.

If a class wants both to have private/protected data and to survive serialization, it should have its own __sleep() method which asks the parent to report its own fields and then adds to the list if applicable.  Like so....

<?php

class BetterClass
{
  private $content;

  public function __sleep()
  {
    return array('basedata1', 'basedata2');
  }

  public function getContents() { ...stuff... }
}

class BetterDerivedClass extends BetterClass
{
  private $decrypted_block;

  public function __sleep()
  {
    return parent::__sleep();
  }

  public function getContents() { ...decrypt... }
}

?>

The derived class has better control over its data, and we don't have to worry about something being stored that shouldn't be.
krisj1010 at gmail.com 09-Jan-2005 12:09
If you are attempting to write an abstract/base class which automates the __sleep process in PHP5 you will run into some trouble if the subclasses which are being serialized have private/protected variables you need to be serialized. 

The reason is, even though get_class($this) within the base class will return the subclass -- get_class_vars(get_class($this)) will *not* return the subclass' protected/private variables.  Which makes sense -- using OO principles. 

However, when automating __sleep it becomes necissary to have access to the private/protected subclass variables because their names have to be returned by __sleep.

So here is the work around:
<?php
public function __sleep()
{
 ... code ...
$sleepVars    = array_keys((array)$this);
return $sleepVars;
}
?>

Even though array_keys includes more information about the variable names than just the variable names -- it still seems to work appropriately.
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