How to replace http:// or www with

Question

I've created this regex

(www|http://)[^ ]+

that match every http://... or www.... but I dont know how to make preg_replace that would work, I've tried

preg_replace('/((www|http://)[^ ]+)/', '<a href="\1">\1</a>', $str);

but it doesn't work, the result is empty string.

Dup: http://stackoverflow.com/questions/507436/how-do-i-linkify-urls-in-a-string-with-php — Sasha Chedygov, Jul 04 '09 at 21:15

score 14 · Accepted Answer · answered Jul 04 '09 at 21:15

14

You need to escape the slashes in the regex because you are using slashes as the delimiter. You could also use another symbol as the delimiter.

// escaped
preg_replace('/((www|http:\/\/)[^ ]+)/', '<a href="\1">\1</a>', $str);

// another delimiter, '@'
preg_replace('@((www|http://)[^ ]+)@', '<a href="\1">\1</a>', $str);

answered Jul 04 '09 at 21:15

Paige Ruten

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Congrats! You’re the only one who doesn’t copy the incorrect regex from chaos. – Gumbo Jul 04 '09 at 21:29
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It doesn't automatically add http:// before www so it's not entirely right: www.google.com will become ... instead of – Thanh Trung Oct 19 '12 at 16:15
not working when on the end of url is
– user956584 Mar 10 '14 at 17:41
At least can you fix your code?? It is not handling https or anything.. -.- – Playdome.io Mar 20 '15 at 12:13
preg_replace('/((www|http:\/\/)[^,\\n ]+)/', '\1', $str); just do little modification to stop replace when encounter "," , "line feed" – chings228 Aug 07 '16 at 08:30

score 2 · Answer 2 · answered Jul 04 '09 at 21:26

When using the regex codes provided by the other users, be sure to add the "i" flag to enable case-insensitivity, so it'll work with both HTTP:// and http://. For example, using chaos's code:

preg_replace('!(www|http://[^ ]+)!i', '<a href="\1">\1</a>', $str);

score 2 · Answer 3 · answered Jul 04 '09 at 21:33

First of all, you need to escape—or even better, replace—the delimeters as explained in the other answers.

preg_replace('~((www|http://)[^ ]+)~', '<a href="\1">\1</a>', $str);

Secondly, to further improve the regex, the $n replacement reference syntax is preferred over \\n, as stated in the manual.

preg_replace('~((www|http://)[^ ]+)~', '<a href="$1">$1</a>', $str);

Thirdly, you are needlessly using capturing parentheses, which only slows things down. Get rid of them. Don't forget to update $1 to $0. In case you are wondering, these are non-capturing parentheses: (?: ).

preg_replace('~(?:www|http://)[^ ]+~', '<a href="$0">$0</a>', $str);

Finally, I would replace [^ ]+ with the shorter and more accurate \S, which is the opposite of \s. Note that [^ ]+ does not allow spaces, but accepts newlines and tabs! \S does not.

preg_replace('~(?:www|http://)\S+~', '<a href="$0">$0</a>', $str);

chaos · Answer 4 · 2009-07-04T21:41:59.977

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preg_replace('!((?:www|http://)[^ ]+)!', '<a href="\1">\1</a>', $str);

When you use / as your pattern delimiter, having / inside your pattern will not work out well. I solved this by using ! as the pattern delimiter, but you could escape your slashes with backslashes instead.

I also didn't see any reason why you were doing two paren captures, so I removed one of them.

Part of the trouble in your situation is that you're running with warnings suppressed; if you had error_reporting(E_ALL) on, you'd have seen the messages PHP is trying to generate about your delimiter problem in your regex.

edited Jul 04 '09 at 21:41

answered Jul 04 '09 at 21:14

chaos

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Funny that most used your incorrect regex for their examples. – Gumbo Jul 04 '09 at 21:30
I imagine we were all copying OP's. Fixed now, in any event. – chaos Jul 04 '09 at 21:42

score 1 · Answer 5 · answered Jul 04 '09 at 21:15

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Your main problem seems to be that you are putting everything in parentheses, so it doesn't know what "\1" is. Also, you need to escape the "/". So try this:

preg_replace('/(www|http:\/\/[^ ]+)/', '<a href="\1">\1</a>', $str);

Edit: It actually seems the parentheses were not an issue, I misread it. The escaping was still an issue as others also pointed out. Either solution should work.

answered Jul 04 '09 at 21:15

Sasha

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I'd just like to add that back references are numbered by the opening parenthesis. For example, in the regexp "T(e(st))", \1 contains "est", and \2 contains "st". – Bravery Onions Jul 04 '09 at 21:53

score 1 · Answer 6 · answered Oct 19 '12 at 15:57

1

If there are multiple url contained in a string a separated by a line break instead of a space, you have to use the \S

preg_replace('/((www|http:\/\/)\S+)/', '<a href="$1">$1</a>', $val);

answered Oct 19 '12 at 15:57

Thanh Trung

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How to replace http:// or www with

6 Answers6