PHP 5.2 to 5.3 Migration: How Do 'self' and 'static' Differ in Late Static Binding?

Late Static Binding: Understanding "self" vs. "static"

In the context of converting a PHP 5.3 library to PHP 5.2, the use of late static binding via "return new static($options)" poses compatibility challenges. Replacing it with "return new self($options)" will not yield the same results. PHP 5.2 lacks support for late static binding.

Understanding the Differences

To clarify, the difference between "self" and "static" lies in their class bindings:

• self: Binds to the class in which the "new" keyword is invoked, regardless of the actual calling class.
• static: (PHP 5.3 ): Binds to the class on which the method is called. If a subclass overrides the method, "static" will refer to the subclass.

Example:

class A {
    public static function get_self() {
        return new self();
    }
}

class B extends A {
    public static function get_self() {
        return new self();
    }
}

$a_self = A::get_self();
$b_self = B::get_self();

// $a_self is an object of class A
// $b_self is an object of class B

In conclusion, when converting code that uses late static binding to PHP 5.2, consider revising the logic to remove this feature. "self" can be used as a workaround in some cases, but it's important to understand its limited binding behavior.

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