Automatically Link URLs and Email Addresses Within Text

gistfile1.php

<?php
function linkify($text) {
    $text = preg_replace('/\b(https?|ftp|file):\/\/[-A-Z0-9+&@#\/%?=~_|!:,.;]*[A-Z0-9+&@#\/%=~_|]/i', '<a href="\0">\0</a>', $text);
    $text = preg_replace('/\b((mailto:)?[A-Z0-9._%+-]+@[A-Z0-9._%-]+\.[A-Z]{2,4})/i', '<a href="mailto:\0">\0</a>', $text);
    return $text;
}
$test_text = "An example of an email address is someone@example.com. Google (http://www.google.com) is the leading search engine! Check out the latest tut @ http://nettuts.com.";

echo linkify($test_text);
?>