Extract URLs from text in PHP

I tried to do as Nobu said, using Wordpress, but to much dependencies to other WordPress functions I instead opted to use Nobu's regular expression for preg_match_all() and turned it into a function, using preg_replace_callback(); a function which now replaces all links in a text with clickable links. It uses anonymous functions so you'll need PHP 5.3 or you may rewrite the code to use an ordinary function instead.

<?php 

/**
 * Make clickable links from URLs in text.
 */

function make_clickable($text) {
    $regex = '#\bhttps?://[^\s()<>]+(?:\([\w\d]+\)|([^[:punct:]\s]|/))#';
    return preg_replace_callback($regex, function ($matches) {
        return "<a href=\'{$matches[0]}\'>{$matches[0]}</a>";
    }, $text);
}

URLs have a quite complex definition — you must decide what you want to capture first. A simple example capturing anything starting with http:// and https:// could be:

preg_match_all('!https?://\S+!', $string, $matches);
$all_urls = $matches[0];

Note that this is very basic and could capture invalid URLs. I would recommend catching up on POSIX and PHP regular expressions for more complex things.

If the text you extract the URLs from is user-submitted and you're going to display the result as links anywhere, you have to be very, VERY careful to avoid XSS vulnerabilities, most prominently "javascript:" protocol URLs, but also malformed URLs that might trick your regexp and/or the displaying browser into executing them as Javascript URLs. At the very least, you should accept only URLs that start with "http", "https" or "ftp".

There's also a blog entry by Jeff where he describes some other problems with extracting URLs.

preg_match_all('/[a-z]+:\/\/\S+/', $string, $matches);

This is an easy way that'd work for a lot of cases, not all. All the matches are put in $matches. Note that this do not cover links in anchor elements (<a href=""...), but that wasn't in your example either.

There are a lot of edge cases with urls. Like url could contain brackets or not contain protocol etc. Thats why regex is not enough.

I created a PHP library that could deal with lots of edge cases: Url highlight.

Example:

<?php

use VStelmakh\UrlHighlight\UrlHighlight;

$urlHighlight = new UrlHighlight();
$urlHighlight->getUrls("this is my friend's website http://example.com I think it is coll");
// return: ['http://example.com']

For more details see readme. For covered url cases see test.

Here is a function I use, can't remember where it came from but seems to do a pretty good job of finding links in the text. and making them links.

You can change the function to suit your needs. I just wanted to share this as I was looking around and remembered I had this in one of my helper libraries.

function make_links($str){

  $pattern = '(?xi)\b((?:https?://|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:\'".,<>?«»“”‘’]))';

  return preg_replace_callback("#$pattern#i", function($matches) {
    $input = $matches[0];
    $url = preg_match('!^https?://!i', $input) ? $input : "http://$input";
    return '<a href="' . $url . '" rel="nofollow" target="_blank">' . "$input</a>";
  }, $str);
} 

Use:

$subject = 'this is a link http://google:ha.ckers.org maybe don't want to visit it?';
echo make_links($subject);

Output

this is a link <a href="http://google:ha.ckers.org" rel="nofollow" target="_blank">http://google:ha.ckers.org</a> maybe don't want to visit it?

<?php
preg_match_all('/(href|src)[\s]?=[\s\"\']?+(.*?)[\s\"\']+.*?/', $webpage_content, $link_extracted);

preview