What does the double colon (::) in PHP means?

https://www.php.net/manual/en/language.oop5.paamayim-nekudotayim.php

The double colon is called the Scope Resolution Operator and is used to ” allows access  to static, constant, and overridden properties or methods of a class.”

//Exemple 1
class MyClass {
    const CONST_VALUE = 'A constant value';
}

$classname = 'MyClass';
echo $classname::CONST_VALUE; // As of PHP 5.3.0

echo MyClass::CONST_VALUE;
//Exemple 2
class OtherClass extends MyClass
{
    public static $my_static = 'static var';

    public static function doubleColon() {
        echo parent::CONST_VALUE . "\n";
        echo self::$my_static . "\n";
    }
}

$classname = 'OtherClass';
$classname::doubleColon(); // As of PHP 5.3.0

OtherClass::doubleColon();