Extension Method¶
An extension method, as found in C#, Kotlin, and Swift, lets a developer add a method to a type without modifying that type’s source and without subclassing it: fun String.shout() = this.uppercase() + '!' adds a shout() method callable on every String, including strings from the standard library. The compiler resolves the call statically, based on the static type of the receiver, and injects it as if it were a real member.
Extension methods are typically used to attach domain-specific behavior to library or built-in types, or to gradually retrofit an interface’s default methods onto existing implementations.
PHP has no extension method mechanism. Methods can only be added to a class by editing its source, extending it, or mixing in a trait, all of which require access to the class declaration or the willingness to create a subclass; a built-in type such as string or a final third-party class cannot receive new methods at all. The common workaround is a free function or a static helper class, called as Str::shout($value) instead of $value->shout().
<?php
// PHP has no way to add shout() to string itself.
final class Str {
public static function shout(string $s): string {
return strtoupper($s) . '!';
}
}
echo Str::shout('hello'); // HELLO!, not 'hello'->shout()
?>
Related : Trait, Class, Mixin, Static Method
