Re: PHP6 return by reference deprecation

[Robert Cummings <robert@xxxxxxxxxxxxx>]

On Sat, 2009-05-02 at 01:07 -0400, Paul M Foster wrote:
> In another thread (which I mercifully declined to highjack), someone
> cited:
> 
> > Taken from http://www.corephp.co.uk/archives/19-Prepare-for-PHP-6.html
> 
> And I read this:
> 
> Both '$foo =& new StdClass()' and 'function &foo' will now raise an
> E_STRICT error.
> 
> I don't use this much, but where I do, it's vital. Typically, I use it
> to ensure a single copy of the $config for an application, as:
> 
> function &get_config() ...
> 
> and/or:
> 
> $cfg =& get_config();
> 
> If this is going away, how do you return things by reference, so as to
> ensure a single copy of something (yes, I know the singleton pattern can
> be used; I do use it as well; it's more complicated)?

PHP5 made it so that objects are always passed by handle. When assigned
or passed as a parameter a copy of the object handle is passed (rather
than a copy of the object itself a la PHP4). Given this, you are in many
ways passing around an implicit reference. It's not exactly a reference,
since there are subtle differences, but the object won't be cloned as it
is in PHP4 using this method. So singletons will work as expected. For
example:

<?php

$a = new StdClass();
$a->a = 'a';

$b = new StdClass();
$b->b = 'b';

$c = new StdClass();
$c->c = 'c';

$d = new StdClass();
$d->d = 'd';

$x = $a;
$x->x1 = 'x1';

$x = $b;
$x->x2 = 'x2';

$y = &$c;
$y->y1 = 'y1';

$y = $d;
$y->y2 = 'y2';

echo "a:\n";
print_r( $a );
echo "b:\n";
print_r( $b );
echo "c:\n";
print_r( $c );
echo "d:\n";
print_r( $d );
echo "x:\n";
print_r( $x );
echo "y:\n";
print_r( $y );

?>

You will get the following output in PHP5:

a:
stdClass Object
(
    [a] => a
    [x1] => x1
)
b:
stdClass Object
(
    [b] => b
    [x2] => x2
)
c:
stdClass Object
(
    [d] => d
    [y2] => y2
)
d:
stdClass Object
(
    [d] => d
    [y2] => y2
)
x:
stdClass Object
(
    [b] => b
    [x2] => x2
)
y:
stdClass Object
(
    [d] => d
    [y2] => y2
)

The difference between references and handles in PHP5 is exemplified
by the output of $a versus the output of $c. In the case of $c because
we assign a reference for $c to $y, then subsequently we assign $d by
value, we essentially completely replace the object $c with $d.
Whereas when we assigned $a by value to $x, then subsequently assigned
$b by value to $x only the handle value was changed.

Cheers,
Rob.
-- 
http://www.interjinn.com
Application and Templating Framework for PHP


-- 
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php