Linkify: turning URLs into clickable links in PHP

Turning links like www.example.com and http://twitter.com into clickable links. Sounds like an easy task, right? We’ll there are a few problems that might arise, especially if the text is already HTML formatted.

This function first takes out all potential dangers, by extracting links and tags and replacing them with a placeholder. It than extracts all URLs and replaces them with a placeholder, storing the full HTML link. At the end it replaces all placeholders with the links and tags.

<?php
 /**
 * Turn all URLs in clickable links.
 * 
 * @param string $value
 * @param array $protocols http/https, ftp, mail, twitter
 * @param array $attributes
 * @param string $mode normal or all
 * @return string
 */
 public function linkify($value, $protocols = array('http', 'mail'), array $attributes = array())
 {
 // Link attributes
 $attr = '';
 foreach ($attributes as $key => $val) {
 $attr = ' ' . $key . '="' . htmlentities($val) . '"';
 }

 $links = array();

 // Extract existing links and tags
 $value = preg_replace_callback('~(<a .*?>.*?</a>|<.*?>)~i', function ($match) use (&$links) { return '<' . array_push($links, $match[1]) . '>'; }, $value);

 // Extract text links for each protocol
 foreach ((array)$protocols as $protocol) {
 switch ($protocol) {
 case 'http':
 case 'https': $value = preg_replace_callback('~(?:(https?)://([^\s<]+)|(www\.[^\s<]+?\.[^\s<]+))(?<![\.,:])~i', function ($match) use ($protocol, &$links, $attr) { if ($match[1]) $protocol = $match[1]; $link = $match[2] ?: $match[3]; return '<' . array_push($links, "<a $attr href=\"$protocol://$link\">$link</a>") . '>'; }, $value); break;
 case 'mail': $value = preg_replace_callback('~([^\s<]+?@[^\s<]+?\.[^\s<]+)(?<![\.,:])~', function ($match) use (&$links, $attr) { return '<' . array_push($links, "<a $attr href=\"mailto:{$match[1]}\">{$match[1]}</a>") . '>'; }, $value); break;
 case 'twitter': $value = preg_replace_callback('~(?<!\w)[@#](\w++)~', function ($match) use (&$links, $attr) { return '<' . array_push($links, "<a $attr href=\"https://twitter.com/" . ($match[0][0] == '@' ? '' : 'search/%23') . $match[1] . "\">{$match[0]}</a>") . '>'; }, $value); break;
 default: $value = preg_replace_callback('~' . preg_quote($protocol, '~') . '://([^\s<]+?)(?<![\.,:])~i', function ($match) use ($protocol, &$links, $attr) { return '<' . array_push($links, "<a $attr href=\"$protocol://{$match[1]}\">{$match[1]}</a>") . '>'; }, $value); break;
 }
 }

 // Insert all link
 return preg_replace_callback('/<(\d+)>/', function ($match) use (&$links) { return $links[$match[1] - 1]; }, $value);
 }

Do you use Twig? Checkout the Jasny Twig extensions, which includes this as well as many other functions and filters.

#php

#links