<?php
    class X {
        public $name;
        public function __construct($name) {
            $this->name = $name;
        }

        # This must be defined in order to have array_diff() working
        #public function __toString() {
        #    return $this->name;
        #}
    }

    $a = new X("A");
    $b = new X("B");
    $c = new X("C");

    $x = array($a, $b, $c);
    $y = array($b);
    $z = array_diff($x, $y); # THIS doesn't work! -> Object of class X could not be converted to string