How to check URL format?

In PHP, how would you detect a URL contained in a string of text and format it to display as a friendly URL?

• For instance, if someone posted something like "This is a pretty cool web site www.google.com/?var1=something&var2=somethingelse&var3=stuff" How would you format it like: "This is a pretty cool web site <a href="http://www.mysite.com/?urlclicked=http://www.google.com/?var1=something&var2=somethingelse&var3=stuff">www.google.com/?var1=something...</a>" The link would first take you to an internal page to record that the link was clicked and then open a new browser window with the destination.

• Answer:

  Use preg_replace() with a regular expression to detect the url and replace it with a link leading to it. You can find a number of more or less permissive url matching regexes online. Here's one example: $text = preg_replace('#(https?\://)?[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(/\S*)?#', '<a href="$1">$1</a>', $text);