Computer Education World

As previously mentioned, one of the larger changes in PHP 5 is that if you
pass objects to a function, they are no longer copied. Although this is usually what you want, it might be that you actually relied on your object being cop-
ied. If that’s the case, your script will no longer work correctly. Look at this
example:
<?php
class str {
var $string;
function str($string) {
$this->string = $string;
}
}
function display_quoted($string)
{
$string->string = addslashes($string->string);
echo $string->string;
}
$s = new str(”Montreal’s Finest Bagels\n”);
display_quoted($s);
echo $s->string;
?>
Because in PHP 4, passing the $s object to the function creates a copy of
the object, the output in PHP 4 is
Montreal\’s Finest Bagels
Montreal’s Finest Bagels
In PHP 5, the object’s handle is passed and the object is actually modi-
fied. Thus, PHP 5 produces different output:
Montreal\’s Finest Bagels
Montreal\’s Finest Bagels
If you want to modify only a copy in PHP 5, one solution is to copy (clone)
the object yourself when you pass it to the function. Do this by using the clone
operator:
display_quoted(clone $s);
Another solution is to disable the new behavior by setting the php.ini
option zend.ze1_compatibility_mode to 1. Or, you can set this option inside your
script itself, but you need to set it before passing the object to a function.

Tip: If your script that relies on the pass-by-copy behavior needs to work
with both PHP 4 and PHP 5, using the clone operator won’t work, because this
operator does not exist in PHP 4. The clone operation will throw an E_ERROR
error when run in PHP 4. In this case, it’s better to use the compatibility mode
setting.