42

It is well documented that PHP5 OOP objects are passed by reference by default. If this is by default, it seems to me there is a no-default way to copy with no reference, how??

function refObj($object){
    foreach($object as &$o){
        $o = 'this will change to ' . $o;
    }

    return $object;
}

$obj = new StdClass;
$obj->x = 'x';
$obj->y = 'y';

$x = $obj;

print_r($x)
// object(stdClass)#1 (3) {
//   ["x"]=> string(1) "x"
//   ["y"]=> string(1) "y"
// }

// $obj = refObj($obj); // no need to do this because
refObj($obj); // $obj is passed by reference

print_r($x)
// object(stdClass)#1 (3) {
//   ["x"]=> string(1) "this will change to x"
//   ["y"]=> string(1) "this will change to y"
// }

At this point I would like $x to be the original $obj, but of course it's not. Is there any simple way to do this or do I have to code something like this

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2 Answers2

78
<?php
$x = clone($obj);

So it should read like this:

<?php
function refObj($object){
    foreach($object as &$o){
        $o = 'this will change to ' . $o;
    }

    return $object;
}

$obj = new StdClass;
$obj->x = 'x';
$obj->y = 'y';

$x = clone($obj);

print_r($x)

refObj($obj); // $obj is passed by reference

print_r($x)
Treffynnon
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    Glad it was helpful. lonesomeday makes a very good point about the `__clone()` magic method some classes might be implementing as well, which is worth noting. – Treffynnon Nov 08 '10 at 12:12
30

To make a copy of an object, you need to use object cloning.

To do this in your example, do this:

$x = clone $obj;

Note that objects can define their own clone behaviour using __clone(), which might give you unexpected behaviour, so bear this in mind.

lonesomeday
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