<?php

var_dump(1 + 1); // int 2
var_dump('1' + '1'); //int 2

class One {
    public function __toString() {
        return '1';
    }
}

var_dump(new One + new One); // Object of class One could not be converted to int  int 2
var_dump((string)new One + (string)new One); // int 2


var_dump(2 + 2); // int 4
var_dump('2' + '2'); // int 4

class Two {
    public function __toString() {
        return '2';
    }
}

var_dump(new Two + new Two); // Notice: Object of class Two could not be converted to int int 2
var_dump((string)new Two + (string)new Two); // int 4