Non-static method x::goo() cannot be called statically

Description

While a non-static method can call a static method, the contrary is not possible. In particular, the non-static method will not be able to have a valid $this variable, since the static call doesn’t provide one.

Example

<?php

class x {
    static function foo() {
        self::goo();
    }

    function goo() {}
}

(new x)->foo();

?>

Solutions

• Make the concrete method static too.

• Find an object to call the non-static method.