Identify external links in a string and add text to them

Dev Shed Forums Sponsor:

January 30th, 2009, 04:46 AM

andyg1

Contributing User

Join Date: Aug 2003

Posts: 235

Time spent in forums: 2 Days 7 h 12 m 32 sec
Reputation Power: 14

Identify external links in a string and add text to them

Guys and girls,

I'm using PHP. I usually like to work these things out myself but I'm totally stuck.

Taking a clump of text e.g. from a CMS entry, I want to check all the links in the text and for those that do not contain

"folder1/folder2"

in the URL path I want to add the text along the lines

"(this link will take you away from this section)"

to the text in the anchor tag, for all links in the text provided.

E.g.

Code:

<a href="some/other/place">my link</a>

would become

Code:

<a href="some/other/place">my link (this link will take you away from this section)</a>

I got as far as this for the expression:

PHP Code:


		
			
 preg_match('/<a.+href=".*folder1/folder2.*".*>.+</a>/i', $testString)

but couldn't even get that to work...

Really appreciate some help with this. Many thanks.

__________________
Time isn't wasted if you're wasted all the time

January 30th, 2009, 11:56 AM

requinix

Still alive

Join Date: Mar 2007

Location: Washington, USA

Posts: 12,698

Folding Points: 417516 Folding Title: Super Ultimate Folder - Level 1

Time spent in forums: 5 Months 1 Week 4 Days 4 h 54 m 57 sec
Reputation Power: 8969

Send a message via Google Talk to requinix

PHP Code:


		
			
 preg_replace('#(<a href="((?!folder1/folder2)[^"])+"[^>]*>)(.*?)</a>#is', '$1$3 (this link will take you away from this section)</a>', $text);

If you need that explained (it's okay if you do) just say something. I would now but I just woke up and I feel weird. Not sick, just... weird. I could probably give a good explanation now but I think it'd be best if I waited a bit before trying to talk at great lengths about something kinda complicated.

[edit] It's amazing what food can do to you. Except for the Raisin Bran aftertaste I feel pretty good.

Code:

(<a href="((?!folder1/folder2)[^"])+"[^>]*>)(.*?)</a>

The important part is the ((?!folder1/folder2)[^"])+. (?!...) means that there should not be a ... at this point. Put it before a [^"] and you get the next character isn't a " and neither is it the start of .... Now that only takes one character, so it gets grouped together with a () and repeated with a +.
(There are a couple other ways of doing the same thing but that's the method I prefer.)

The rest is simple if you know that .*? is the same as .* except it matches as few characters as possible.

__________________
Site rules and FAQ | Project Suggestions | mod_rewrite guide | PHP New User Guide and FAQ - PHP Stickies | Regex Resources

Last edited by requinix : January 30th, 2009 at 01:48 PM.

Identify external links in a string and add text to them

Developer Shed Advertisers and Affiliates