I want to auto-magically change the color of a URL in the middle

Found on the digitalpoint forums at http://forums.digitalpoint.com/showthread.php?t=687808

I want to auto-magically change the color of a URL in the middle, like this

domain_name.com

There is no www so the period can be used as delimiter. The URL is generated by PHP so I can not simply use HTML.

Using Regular Expressions in PHP we can identify the part of the text that contains the domain name and wrap it in a span.

Test String: “here is the text surrounding dom-ain.com text and a generic .com name alongwith do.main.net, domain.org and del.co.uk”

Using preg_replace with regular expressions in PHP

<?php

$string = ‘here is the text surrounding dom-ain.com text and a generic .com name alongwith do.main.net, domain.org and del.co.uk’;
$pattern = ‘/([0-9a-zA-Z.\-]+)+(.com|.net|.org|.co.uk)/’;
$replacement = ‘<span style=”color:#F00″>${1}</span>${2}’;
echo preg_replace($pattern, $replacement, $string);

?>

Output: “here is the text surrounding dom-ain.com text and a generic .com name alongwith do.main.net, domain.org and del.co.uk”

How its done

From http://us.php.net/preg-replace

preg_replace — Perform a regular expression search and replace

mixed preg_replace( mixed $pattern ,mixed $replacement ,mixed $subject [,int $limit [,int &$count ]] )

Searches $subject for matches to $pattern and replaces them with $replacement.

The $string will be the text that contains your domain names.

$pattern is a regular expression pattern I constructed following the handy cheat sheet at http://regexlib.com/CheatSheet.aspx and testing it online at http://regexlib.com/RETester.aspx

Deconstructing the regular expression
‘/
- start

([0-9a-zA-Z.\-]+)+
- match all characters from 0-to-9 a-to-z A-toZ and ‘.’ and ‘-’. These are the valid characters for domain names. The ‘+’ signs mean atleast 1 or more of that sequence must be matched

(.com|.net|.org|.co.uk)
- Very literally a ‘.com’, ‘.org’ or ‘.co.uk’ must follow the previous set of characters. You can add additional TLDs here, seperated by a pipe(’|') which acts as an ‘OR’.

/’
- end

The $replacement is a string with the span tag wrapped around ${1} and ${2}, these represent the 1st and 2nd matched sequences, for example ‘domain’ and ‘.com’. ${0} would match the entire ‘domain.com’ string.

Regular Expressions are HARD.

Even for advanced users, here are some resources to help you get started using them.

http://regexlib.com/CheatSheet.aspx - Cheat Sheet
http://regexlib.com/RETester.aspx - Online Tester
http://www.zytrax.com/tech/web/regex.htm - A Simple User Guide
http://www.amk.ca/python/howto/regex/ - Detailed Regular Expression HOWTO