ive never used regex expressions till now and had loads of difficulty trying to convert a [url]link here[/url] into an href for use with posting messages on a forum, heres what i manage to come up with:
$patterns = array(
"/\[link\](.*?)\[\/link\]/",
"/\[url\](.*?)\[\/url\]/",
"/\[img\](.*?)\[\/img\]/",
"/\[b\](.*?)\[\/b\]/",
"/\[u\](.*?)\[\/u\]/",
"/\[i\](.*?)\[\/i\]/"
);
$replacements = array(
"<a href=\"\\1\">\\1</a>",
"<a href=\"\\1\">\\1</a>",
"<img src=\"\\1\">",
"<b>\\1</b>",
"<u>\\1</u>",
"<i>\\1</i>"
);
$newText = preg_replace($patterns,$replacements, $text);
at first it would collect ALL the tags into one link/bold/whatever, until i added the "?" i still dont fully understand it... but it works :)