(PECL runkit >= 0.7.0)
runkit_constant_add — Similar to define(), but allows defining in class definitions as well
constnameName of constant to declare. Either a string to indicate a global constant, or classname::constname to indicate a class constant.
valueNULL, Bool, Long, Double, String, or Resource value to store in the new constant.
成功时返回 TRUE， 或者在失败时返回 FALSE。