Neil Hillman

If like me, you often need to use regular expressions, but still after over 10 years of using them can waste an entire morning just trying to write a simple search and replace, here are some really useful snippets I have used along the way.

To match an HTML link within a string, and to isolate the inner HTML, (whatever occurs between the opening and closing anchor tags), use:

<?php
preg_match('#<a\s+.*?href=[\'"]([^\'"]+)[\'"]\s*
    (?:title=[\'"]([^\'"]+)[\'"])?.*?>((?:(?!</a>).)*)</a>#i', $input, $match);

// $input - A STRING CONTAINING AN ANCHOR LINK WITH INNER HTML
$input = 'This is some text containing a linked image <a
    href="http://www.google.com"><img src="google.jpg" alt="Google"
    width="200" height="50" /></a>. Goodbye.';

// $match[0] RETURNS THE ENTIRE LINK INCLUDING THE INNER HTML AND ANCHOR TAGS
$match[0] == '<a href="http://www.google.com"><img src="google.jpg"
    alt="Google" width="200" height="50" /></a>';

// $match[1] RETURNS JUST THE ANCHOR LINK
$match[1] == 'http://www.google.com';

// $match[2] RETURNS THE INNER HTML, IN THIS CASE, JUST THE IMAGE TAG
$match[2] == '<img src="google.jpg" alt="Google" width="200" height="50" />';
?>

To match an email address, and to isolate either the username or domain name part of the address, use:

<?php
preg_match('#([a-z0-9&\-_.]+?)@([\w\-]+\.([\w\-\.]+\.)*[\w]+)#i',
    $input, $match);

// $input - A STRING CONTAINING AN EMAIL ADDRESS
$input = 'My email address is spam-a-lot@mydomain.com. Write me!';

// $match[0] RETURNS ONLY THE VALID EMAIL ADDRESS
$match[0] == 'spam-a-lot@mydomain.com';

// $match[1] RETURNS ONLY THE USERNAME PART
$match[1] == 'spam-a-lot';

// $match[2] RETURNS ONLY THE DOMAIN NAME PART
$match[2] == 'mydomain.com';
?>

To match an email address, and replace it with a clickable link to the email address, use:

<?php
$ret = preg_replace("#([a-z0-9&\-_.]+?)@([\w\-]+\.([\w\-\.]+\.)*[\w]+)#i",
    "\\1<a href="mailto:\\2@\\3">\\2@\\3</a>", $input);

// $input - A STRING CONTAINING AN EMAIL ADDRESS
$input = 'My email address is spam-a-lot@mydomain.com. Write me!';

// $ret - RETURNED STRING CONTAINING A CLICKABLE EMAIL LINK
$ret == 'My email address is <a
    href="mailto:spam-a-lot@mydomain.com">spam-a-lot@mydomain.com</a>.
    Write me!';
?>