Serializing a reference in PHP

Question

I would like to know why my serialization in php does not work as expected:

<?
$x = "whatever...";
$y = array(&$x, "test, 1-2, 1-2...", &$x);
$yy = unserialize(serialize(&$y));
$y[0] = "blah";
echo($yy[0]); // prints 'whatever', was expecting 'blah'
?>

Answer 1

The & is ignored by serialize.

It seems like you are trying to create a symbol table alias (reference) from y to yy, but you cannot do that here. When you pass &y to serialize, it does not treat the passed value as a reference or serialize in line. Moreover, it returns an entirely new value, not a reference to the original value. You would have to create the alias separately:

$yy = &$y;
$yy = unserialize(serialize($y));

I'm also not really sure what you're trying to do either, or what it has to do with serialization.

Answer 2

As Explosion Pills' answer states, unserialize "returns an entirely new value". However, serialization will maintain "relative" references. (Technically, there is no such thing as a relative reference in PHP, but its a good way to conceptualize it.)

If you collect your referenced and referencing variables in an array, serializing the array will save the reference relationship. It won't maintain the original reference, but will automatically recreate it in the context of the new array returned by unserialize.

$vars = array();
$vars['x'] = 'initval';
$vars['xref'] =& $vars['x'];
$vars2 = unserialize( serialize( $vars ) );
$vars2['x'] = 'newval';
echo $vars2['xref']; // prints "newval"

It works the same way for internal references in objects.