interface

<?php

interface parentClass1{

    function calc($a, $b); //Can not set access modifier

}

interface parentClass2{

    function sub($c, $d);

}

class childClass implements parentClass1, parentClass2{

    public function calc($a, $b){

        echo $a + $b;

    }

    public function sub($c, $d){

        echo $c - $d;

    }

}

$test = new childClass();

$test->calc(20,35);
echo "<br>";

$test->sub(75, 30);

?>