PHP 5.2 vs. 5.3: Can 'new self' Replace 'new static'?

Late Static Binding: Analyzing "new self" and "new static"

When transitioning a PHP library from version 5.3 to 5.2, one encounters the issue of late static binding, exemplified by code snippets like "return new static($options)". In PHP 5.2, such syntax is unavailable. This article aims to explore the nuances between "new self" and "new static" and determine if "new self" provides equivalent functionality in a PHP 5.2 environment.

The Distinction Between "new self" and "new static"

In PHP 5.2, "self" references the class in which the "new" keyword is explicitly declared. In contrast, "static", with its late static binding capabilities in PHP 5.3, points to the class from which the method was invoked within an inheritance hierarchy.

To illustrate this distinction, consider the following class structure:

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

    public static function get_static() {
        return new static();
    }
}

class B extends A {}

In this example, the methods "get_self" and "get_static" are inherited in class B from class A. Invoking "get_self" in B will return an instance of class A, as the "self" reference binds to the class where the method is defined. However, invoking "get_static" in B will return an instance of class B, as "static" in late static binding will resolve to the class from which the method is called.

Applying "new static" to PHP 5.2

Unfortunately, there is no direct workaround to implement PHP 5.3's "new static" functionality in PHP 5.2. The "return new self($options)" statement will not yield the same results as it did in PHP 5.3, as "self" always refers to the class where the method is defined rather than the class from which it is invoked.

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