Posted by Chung Leong on 01/13/06 05:01

Here's a little brain teaser distilled from a bug that took me a rather
long time to figure out. The two functions in the example below behave
differently. The difference is easy to spot, of ocurse. The challenge
is correctly explaining why this is so. Why does the second function
seemingly corrupt the cloned copy of an object?

Sample code:

<?php

// uncomment the clone operator for PHP 5

function Bobcat(&$obj) {
$clone = /* clone */ $obj;
$obj->attributes['Length'] = 0;
$obj->data = "";
return $clone;
}

function BritneySpear(&$obj) {
$attr =& $obj->attributes;
$clone = /* clone */ $obj;
$obj->attributes['Length'] = 0;
$obj->data = "";
return $clone;
}

$data = "This is a test";

$obj1->attributes = array('Length' => strlen($data));
$obj1->data = $data;
$clone1 = Bobcat($obj1);
print_r($clone1);

$obj2->attributes = array('Length' => strlen($data));
$obj2->data = $data;
$clone2 = BritneySpear($obj2);
print_r($clone2);

?>

Result:

stdClass Object
(
[attributes] => Array
(
[Length] => 14
)

[data] => This is a test
)
stdClass Object
(
[attributes] => Array
(
[Length] => 0
)

[data] => This is a test
)

[Back to original message]