<?php
class foo {
     var $bar, $is_clone = 0;
    function baz($val) {
        $this->bar = $val;
    }
    function __clone()
    {
        $this->is_clone = 1;
    }
}

$a = new foo();
$b = clone $a; // make $b contain a separate copy of $a

echo $b->is_clone; // will print 1
?>