Regular Expression URLS to Links

Question

Im using the following regex to convert urls to href links. It works great, however ive found a bug with it when using style tags which have a background image.

 /** * Convert urls in a string to a html link * @return string */ public static function ConvertUrlsToHtml($str) { $str = preg_replace( '@(?<![.*">])\b(?:(?:https?|ftp|file)://|[a-z]\.)[-A-Z0-9+&#/%=~_|$?!:,.]*[A-Z0-9+&#/%=~_|$]@i', '<a href="\0">\0</a>', $str); return $str; }

If i use the following...

<div class="inner-left" style="background-image: url(http://www.somewebsite/background.jpg);"></div>

It converts the background image to a href too.

Does anyone know how i can tweak the regex to ignore the style tags?

Use a DOM Parser to parse HTML, regex gets a nightmare to handle. — Connor Gurney
– Connor Gurney, Commented Apr 8, 2013 at 15:04
That doesnt help. Using DOMDocument doesnt work here, because its not neccessarily html. Its just a string which may or may not contain any html. So therefore, i need to find all instances of a URL in any given string, be it html or not. Then i need to create the html. — samsamm777
– samsamm777, Commented Apr 8, 2013 at 15:08
@SamuelDavidHudson: At least, using a HTML Parser will take the text in HTML (which should not be replaced) out of the way and let you work on the text alone. — nhahtdh
– nhahtdh, Commented Apr 8, 2013 at 15:20
Try adding another negative lookbehind: preg_replace( '@(?<!url\()(?<![.*">])... — Kenneth K.
– Kenneth K., Commented Apr 8, 2013 at 15:21

Tchoupi · Accepted Answer · 2013-04-08 16:36:59Z

You can start by removing HTML tags, because you don't want to replace URLs inside tags. It is true for style=, it is also true for <img src=... and <a href=...> and so on.

function ConvertUrlsToHtml($str) { $strNoTags = strip_tags($str); if (preg_match_all( '@(?<![.*">])\b(?:(?:https?|ftp|file)://|[a-z]\.)[-A-Z0-9+&#/%=~_|$?!:,.]*[A-Z0-9+&#/%=~_|$]@i', $strNoTags, $matches)) { foreach ($matches[0] as $match) { $str = str_replace($match, "<a href=\"$match\">$match</a>", $str); } } return $str; }

What it does:

Remove the tags
Get all URL in the tag free string
Replace found URLs by a link in the original string

As it was commented, you could always try a HTML parser first to extract the text instead of strip_tags.

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