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16 years ago

in addition to what 'jw at jwscripts dot com' wrote about unset; it can also be used to "detach" the variable alias so that it may work on a unique piece of memory again.

here's an example

<?php
define('NL', "\r\n");

$v1 = 'shared';
$v2 = &$v1;
$v3 = &$v2;
$v4 = &$v3;

echo 'before:'.NL;
echo 'v1=' . $v1 . NL;
echo 'v2=' . $v2 . NL;
echo 'v3=' . $v3 . NL;
echo 'v4=' . $v4 . NL;

// detach messy
$detach = $v1;
unset($v1);
$v1 = $detach;

// detach pretty, but slower
eval(detach('$v2'));

$v1 .= '?';
$v2 .= ' no more';
$v3 .= ' sti';
$v4 .= 'll';

echo NL.'after:'.NL;
echo 'v1=' . $v1 . NL;
echo 'v2=' . $v2 . NL;
echo 'v3=' . $v3 . NL;
echo 'v4=' . $v4 . NL;

function detach($v) {
    $e = '$detach = ' . $v . ';';
    $e .= 'unset('.$v.');';
    $e .= $v . ' = $detach;';
    return $e;
}
?>

output {
before:
v1=shared
v2=shared
v3=shared
v4=shared

after:
v1=shared?
v2=shared no more
v3=shared still
v4=shared still
}

http://www.obdev.at/developers/articles/00002.html says there's no such thing as an "object reference" in PHP, but with detaching it becomes possible.

Hopefully detach, or something like it, will become a language construct in the future.
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