Find and replace text URLs by HTML clickable links.

htmllinks.php

<?php

/**
 * Finds and replaces text URLs by HTML clickable links.
 *
 * @author     Honza Javorek http://www.javorek.net/
 * @copyright  Copyright (c) 2008 Jan Javorek
 * @license    New BSD License
 */
class HtmlLinks {

	/**
	 * Max length of link.
	 *
	 * @var int
	 */
	public $limit = 30;

	/**
	 * Characters trimmed from the right end of link.
	 *
	 * @var array
	 */
	public $marks = array(',', '.', '!', '?', '"', '\'', ';', ':', '&');

	/**
	 * Supported protocols.
	 *
	 * @var array
	 */
	public $protocols = array('http://', 'https://', 'ftp://');

	public function __construct() {
	}
	
	/**
	 * Replaces regular expression matches by a clickable link.
	 *
	 * @param array $matches
	 * @return string
	 */
	private function replaceLink(array $matches) {
		$match = $matches[0];
		$protocol = $matches[2];
		$mark = substr($match, -1, 1);

		// marks at the end
		if (in_array($mark, $this->marks)) {
			$match = substr($match, 0, -1);
		} else {
			$mark = '';
		}

		// length
		$len = strlen($match);

		// http at the beginning
		$http = '';
		if (!in_array($protocol, $this->protocols)) {
			$http = 'http://';
		}

		// length handling and creating the link
		if ($len > $this->limit) {
			return "<a href=\"$http$match\">" . substr($match, 0, $this->limit) . "&hellip;</a>$mark";
		} else {
			return "<a href=\"$http$match\">$match</a>$mark";
		}
	}

	/**
	 * Replaces text URLs by HTML clickable links in given string.
	 *
	 * @param string $s
	 * @return string
	 */
	public function process($s) {
		return preg_replace_callback(
			'~(?<![=\\"\\\'\\/])((([a-zA-Z]+:\\/\\/)|(www\\.))[^\\s]+)~i',
			array($this, 'replaceLink'), // see http://www.php.net/manual/en/language.pseudo-types.php#language.types.callback
			$s
		);
	}

}