MethodSignatureMismatch

An overriding method has a signature incompatible with the parent’s.

Example

<?php
class Base {
    public function process(string $input): string { return $input; }
}

class Child extends Base {
    public function process(int $input): string { return (string) $input; } // parameter type changed
}

How to fix

Make the overriding method’s signature compatible with the parent’s (contravariant parameters, covariant return types).