zend.ze1_compatibility_mode:
<?php
    ini_set
('zend.ze1_compatibility_mode''1');
    
    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 
$linux->name"\n"$win->name;
?>

output:
linux
windows