PHP check if string contains url without http://

Question

What is the best way to find if a string contains a url?

I'm writing a chatbox and need to deny the posting of urls in it...

if(preg_match('/[a-zA-Z]+:\/\/[0-9a-zA-Z;.\/?:@=_#&%~,+$]+/', $clean_message, $matches))
{
die('INVALID!');
}

seems to do the trick for urls that contain http:// but i need to also be able to deny urls such as youtube.com and if an ipaddress is posted etc..

I need to keep the chatbox clean from users spamming urls!

Why bother? You'll never stop stuff like www [dot] youtube [dot] com. Filter for automated spam postings, and let it go? — Brad
– Brad, Commented Nov 24, 2011 at 1:10
I can spam a URL like this: s t a c k o v e r f l o w . c o m — Oliver Charlesworth
– Oliver Charlesworth, Commented Nov 24, 2011 at 1:11
You can do like Office Communicator and just add _ to known web protocols. Like: _http://www.example.com. Then it's up to the person on the other end to follow through. — Jared Farrish
– Jared Farrish, Commented Nov 24, 2011 at 1:12
@E3pO: Whatever rule you come up with, I can come up with a way to circumvent it. — Oliver Charlesworth
– Oliver Charlesworth, Commented Nov 24, 2011 at 1:16

Godwin · Accepted Answer · 2011-11-24 01:20:22Z

5

Probably the best you can do is something like:

/[\w\d\.]+\.(com|org|ca|net|uk)/

and add in all other common suffixes. Doing something like:

/[\w\d\.]+\.[\w\d]{1,3}/

might be too generic but would catch pretty much anything that looked like a URL.

edited Nov 24, 2011 at 1:20

answered Nov 24, 2011 at 1:15

Godwin

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4 Comments

E3pO Over a year ago

That works great now but we run into the issue of people saying things such as "wow.that.is.cool!"

Godwin Over a year ago

wow.that.is.cool could be a url, I don't think there's any way to know that it's not.

Godwin Over a year ago

You're going to have to decide where to draw the line between letting some urls through, and not letting users enter something they want that isn't a url. You're going to end up with a bit in each anyway you do it.

Godwin Over a year ago

Actually I just realized there's another issue, this would block "100.00". You should probably replace the [\w\d\.] with something like [\w\d\.]*\w[\w\d\.]*

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