I need help with preg_replace and slashes

[ChaoticAzure]

I am trying out preg_replace to replacing relative URL paths with absolute URL paths, here's what I have so far:

<?php
$search = 'href="@/@';
$replace = 'http://google.com/';
$link = '<a id=1a class=q href="/imghp?hl=en&tab=wi&ie=UTF-8">Google Image Search Linky</a>';
$absolute = preg_replace($search, $replace, $link);
echo $absolute;
?>

I want to get

<a id=1a class=q href="http://google.com/imghp?hl=en&tab=wi&ie=UTF-8">Google Image Search Linky</a>

But, I get the following error:

Warning: preg_replace(): Delimiter must not be alphanumeric or backslash in pregtest.php on line 5

Could someone please help me and explain this to me please? 😕

[FatalError]

You have to have a character (most of the time it is a forward slash, '/') at the beginning and end of the $search string. I use #, since it's the most unlikely character to have in a search (and it's easily visible). Keep in mind that you have to escape that character everywhere else. So if you use /, you have to escape the one you currently have (near "@/@).