Replace all urls in string not matching pattern in php

Question

I'm using this code to replace urls in a string

preg_replace('#<a.*?>(.*?)</a>#i', '\1', $text)

How do I do the same thing, but keeping urls that match a certain pattern (ie start with a domain I want to keep)?

Update

Turns out that the urls I want to keep include relative urls, so I now want to eliminate all urls that don't match the given url pattern and are not relative links.

elixenide · Accepted Answer · 2014-01-29 22:13:08Z

1

You need a negative look-ahead assertion:

preg_replace('#<a(?![^>]+?href="?http://keepthisdomain.com/foo/bar"?).*?>(.*?)</a>#i', '\1', $text);

Edit: If you want to match only relative domains, the logic is the same. Just take out the protocol and domain name:

preg_replace('#<a(?![^>]+?href="?/?path/to/foo/bar"?).*?>(.*?)</a>#i', '\1', $text);

The ? after " and / means that those characters are optional. So, the second example will work for either path/to/foo/bar or /path/to/foo/bar.

edited Jan 29, 2014 at 22:13

answered Jan 29, 2014 at 21:07

elixenide

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7 Comments

lordmj Over a year ago

How do I get this to keep relative urls in addition to the ones matching the keep domain?

elixenide Over a year ago

Just tweak it; see my edit. Please accept the answer if you found it helpful!

lordmj Over a year ago

Was also wondering how to replace urls that appear in the text even if they are not hyperlinks. So a free form url would be stripped out as well. Keeping urls that match the keepthisdomain of course. I will be applying the hyperlink strip regex before the free form strip regex

elixenide Over a year ago

@lordmj The logic here is the same. Just use the first version, without the portions relevant to anchor tags, like so: preg_replace('#(?!http://keepthisdomain.com/foo/bar)http://[^<>\s]*#i', '\1', $text); Note: this may require some tweaking, because it would apply to everything, not just plain text. So, it might nuke some img tags, for example. You would need to modify the "good" URL pattern to preserve anything you want to keep.

lordmj Over a year ago

Revisitng this again. Now I want to remove the same hyperlinks as before. But if it has the attribute rel="shadowbox[a]" I want to keep the hyperlink.

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