This is something which I get asked quite often, how to make it possible for a user to use UBB tags to format their text, this is a function which I wrote ages ago, but still use whenever I want UBB to be enabled.

<?php
function ubb_tags($string){
while(preg_match("/\[color=(\w+)\](.+?)\[\/color\]/i",$string)){
$string = preg_replace("/\[color=(\w+)\](.+?)\[\/color\]/i","<font color=$1>$2</font>",$string);
}
while(preg_match("/\[colour=(\w+)\](.+?)\[\/colour\]/i",$string)){
$string = preg_replace("/\[colour=(\w+)\](.+?)\[\/colour\]/i","<font color=$1>$2</font>",$string);
}
while(preg_match("/\[b\](.+?)\[\/b\]/i",$string)){
$string = preg_replace("/\[b\](.+?)\[\/b\]/i","<b>$1</b>",$string);
}
while(preg_match("/\[url=(\w+)\](.+?)\[\/url\]/i",$string)){
$string = preg_replace("/\[url=(\w+)\](.+?)\[\/url\]/i","<a href='$1'>$2</a>",$string);
}
while(preg_match("/\[i\](.+?)\[\/i\]/i",$string)){
$string = preg_replace("/\[i\](.+?)\[\/i\]/i","<i>$1</i>",$string);
}
while(preg_match("/\[u\](.+?)\[\/u\]/i",$string)){
$string = preg_replace("/\[u\](.+?)\[\/u\]/i","<u>$1</u>",$string);
}
while(preg_match("/\[img\](.+?)\[\/img\]/i",$string)){
$string = preg_replace("/\[img\](.+?)\[\/img\]/i","<img src='$1'>",$string);
}
while(preg_match("/\[url\](.+?)\[\/url\]/i",$string)){
$string = preg_replace("/\[url\](.+?)\[\/url\]/i","<a href='$1'>$1</a>",$string);
}
while(preg_match("/\[center\](.+?)\[\/center\]/i",$string)){
$string = preg_replace("/\[center\](.+?)\[\/center\]/i","<center>$1</center>",$string);
}
return $string;
}

I've done a lot of experimentation with making my own UBB tags, which is pretty entertaining, but those are just the usual. To enable UBB tags, put that function round the information which you want the tags to apply to. For example if the text is stored in $post, then you would use the line

$post = ubb_tags($post);

so that the ubb tags would be applied when you print $post further down the page.

- Boag