php youtube and links regex are combining and in turn rendering useless - php

Question

i have a posting feature on my site that can embed links and youtube videos. the problem is, that the two clash together, and the youtube iframe ends up being a 404 page on my site. my codes for the youtube videos and links are below, but im not sure how to stop them from combining and ruining it.
by combining, i mean this http://www.youtube.com/watch?v=VhqiT2nWCVU turns to
<iframe src="http://www.youtube.com/watch?v=VhqiT2nWCVU">
which then turns into
<iframe src="">
sorry if i am unclear in any way. my codes are below.
function youtube($string)
{
return preg_replace(
'#(http://(www.)?youtube.com)?/(v/|watch\?v\=)([-|~_0-9A-Za-z]+)&?.*?#i',
'<iframe title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/$4?rel=0" frameborder="0" allowfullscreen></iframe>',
$string
);
}
$posted = youtube($posted);
$rexProtocol = '(https?://)?';
$rexDomain = '((?:[-a-zA-Z0-9]{1,63}\.)+[-a-zA-Z0-9]{2,63}|(?:[0-9]{1,3}\.){3}[0-9]{1,3})';
$rexPort = '(:[0-9]{1,5})?';
$rexPath = '(/[!$-/0-9:;=#_\':;!a-zA-Z\x7f-\xff]*?)?';
$rexQuery = '(\?[!$-/0-9:;=#_\':;!a-zA-Z\x7f-\xff]+?)?';
$rexFragment = '(#[!$-/0-9:;=#_\':;!a-zA-Z\x7f-\xff]+?)?';
// Solution 1:
function callback($match)
{
// Prepend http:// if no protocol specified
$completeUrl = $match[1] ? $match[0] : "http://{$match[0]}";
return '<a href="' . $completeUrl . '">'
. $match[2] . $match[3] . $match[4] . '</a>';
}
$posted = preg_replace_callback("&\\b$rexProtocol$rexDomain$rexPort$rexPath$rexQuery$rexFragment(?=[?.!,;:\"]?(\s|$))&",
'callback', $posted);

Answer 1

A popular solution to this problem is to use placeholders. On your first pass you turn all YouTube links into a placeholder, for example:
{{youtube:VhqiT2nWCVU}}
After that you run your normal link converter. And at the end your run yet another regex to turn all your palceholders into youtube embeds.