Why Do Calls to Non-Static Methods Using PHP\'s Double Colon Syntax Fail?

Calling Non-Static Methods Using Double Colon Syntax

In PHP, it's possible to call non-static methods using the syntax of static methods, class::method. However, why is it that such calls fail?

Consider the following example:

class Teste {
    public function fun1() {
        echo 'fun1';
    }
    public static function fun2() {
        echo "static fun2";
    }
}

Calling Teste::fun2() works because it's a static method, but calling Teste::fun1() raises an error.

The explanation lies in PHP's loose handling of static vs. non-static methods. When a non-static method is called statically from within a non-static method of class C, $this inside the non-static method ns refers to the instance of C.

For example:

class A {
    public function test() {
        echo $this->name;
    }
}

class C {
    public function q() {
        $this->name = 'hello';
        A::test();
    }
}

$c = new C;
$c->q(); // prints hello

Although this may cause unexpected behavior, it's not an error unless strict error reporting is enabled. Therefore, calling non-static methods statically using double colon syntax is discouraged, as it can lead to errors or confusing behavior.

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