How to mimic Stack Overflow Auto-Link Behavior

Question

With PHP how can I mimic the auto-link behavior of Stack Overflow (which BTW is awesomely cool)?

For instance, the following URL:

http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior

Is converted into this:

<a title="how to mimic stackoverflow auto link behavior" rel="nofollow" href="http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior">stackoverflow.com/questions/1925455/…</a> 

I don't really care for the title attribute in this case.

---

And this:

http://pt.php.net/manual/en/function.base-convert.php#52450

Is converted into this:

<a rel="nofollow" href="http://pt.php.net/manual/en/function.base-convert.php#52450">pt.php.net/manual/en/…</a> 

How can I make a similar function in PHP?

PS: Check my comments on this question for some more examples and behaviors.

Answer 1

Try this out. The URL-matching regex pattern is from Daring Fireball.

/**  * Replace links in text with html links  *  * @param  string $text  * @return string  */ function auto_link_text($text) {    // a more readably-formatted version of the pattern is on http://daringfireball.net/2010/07/improved_regex_for_matching_urls    $pattern  = '(?i)\b((?:[a-z][\w-]+:(?:/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:\'".,<>?«»“”‘’]))';     $callback = create_function('$matches', '        $url       = array_shift($matches);        $url_parts = parse_url($url);         $text = parse_url($url, PHP_URL_HOST) . parse_url($url, PHP_URL_PATH);        $text = preg_replace("/^www./", "", $text);         $last = -(strlen(strrchr($text, "/"))) + 1;        if ($last < 0) {            $text = substr($text, 0, $last) . "&hellip;";        }         return sprintf(\'<a rel="nofollow" href="%s">%s</a>\', $url, $text);    ');     return preg_replace_callback($pattern, $callback, $text); } 

Input Text:

This is my text.  I wonder if you know about asking questions on StackOverflow:  Check This out http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior   Also, base_convert php function? http://pt.php.net/manual/en/function.base-convert.php#52450  http://pt.php.net/manual/en/function.base-convert.php?wtf=hehe#52450 

Output Text:

This is my text.  I wonder if you know about asking questions on StackOverflow:  Check This out <a rel="nofollow" href="http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior">stackoverflow.com/questions/1925455/&hellip;</a>   Also, base_convert php function? <a rel="nofollow" href="http://pt.php.net/manual/en/function.base-convert.php#52450">pt.php.net/manual/en/&hellip;</a>  <a rel="nofollow" href="http://pt.php.net/manual/en/function.base-convert.php?wtf=hehe#52450">pt.php.net/manual/en/&hellip;</a>