LinkLocator.php

<?php
class URL
{
	public function auto($string, $type = 'both', $attr = false, $echo = false)
	{
		if ($type == 'both' || $type == 'url')
		{
			$regex = '/(?<anchor><a(?:\s+(?<attr>(?:\S+?=(?:(?:\'.*?\')|(?:".*?")\s*))+))?>(?<text>.*?)<\/a\s*>)|(?<!>)(?<url>(?<proto>https?:\/{2})(?<domain>[a-zA-Z0-9\-.]+\.[a-zA-Z]{2,3})(?<path>\/\S*)?)/i';
			return preg_replace_callback($regex, function($matches)
			{
				if (strlen($matches['anchor']) > 0)
				{
					if (true) //filter attributes?
					{
						$attributeString = null;
						
						if (strlen($matches['attr']) > 0)
						{
							preg_match_all('/' . '(?:\S+?=(?:(?:\'.*?\')|(?:".*?")\s*))' . '/i', $matches['attr'], $attributes);
							foreach ($attributes[0] as $attribute)
							{
								$attibuteSplit = explode('=', $attribute);
								if (in_array($attibuteSplit[0], array('href')))
								{
									$attributeString .= ' ' . $attribute;
								}
							}
						}
					}
					else
					{
						$attributeString = ' ' . $matches['attr'];
					}
					
					return '<a' . $attributeString . '>' . $matches['text'] . '</a>';
				}
				else
				{
					$url =  $matches['proto'] . $matches['domain'] . $matches['path'];
					return '<a href="' . $url . '">' . $url . '</a>';
				}
			}, $string);
		}
	}
}