<?php
    class OS {
        var $name;
        function OS($name) {
            $this->name = $name;
        }
    }

    function changeName(&$obj, $name) {
        $obj->name = $name;
    }

    $linux = new OS('linux');
    $win = $linux;
    changeName($win, 'windows');
    echo $linux->name. "<br />\n";
    echo $win->name;
?>

<?php
    class OS {
        var $name;
        function OS($name) {
            $this->name = $name;
        }
    }

    function changeName($obj, $name) {
        $obj->name = $name;
    }

    $linux = new OS('linux');
    $win = clone $linux;
    changeName($win, 'windows');
    echo $linux->name. "\n";
    echo $win->name;
?>