Can I Use the Double Colon (::) Operator to Call Non-Static Methods in PHP?

Non-Static Method Invocation Using Double Colon (::)

In PHP, non-static methods cannot be invoked using the syntax of static methods (class::method). This behavior stems from the distinct nature of static and non-static methods.

Static methods are defined within a class but do not require an instance of the class to be called. They are typically used for utility functions or constants. In contrast, non-static methods require an instance of the class to be created before they can be accessed.

The double colon (::) syntax is reserved for invoking static methods. When you attempt to invoke a non-static method using this syntax, PHP raises an error. This error is not a configuration issue but rather a fundamental limitation of the language.

Example:

class Teste {

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

// Attempt to invoke non-static method using double colon syntax
Teste::fun1(); // Raises error

// Invocation of static method using double colon syntax
Teste::fun2(); // Works as expected

Special Considerations

While non-static methods cannot be invoked using the double colon syntax, there is one exception to this rule. Within a non-static method, you can invoke a non-static method of the same class using the following syntax:

$this->nonStaticMethod();

In this context, the $this keyword represents the current instance of the class, allowing you to access non-static methods from within the same instance. Additionally, if you call a non-static method statically from within a non-static method of the same class, the $this inside the invoked method will refer to the instance of the calling class.

Example:

class A {

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

class C {

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

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

It's important to note that this exception to the rule is not always desirable. Strict error reporting may result in errors if you attempt to use this syntax unintentionally.

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