Remove all non-alphanumeric characters using preg_replace

Question

How can I remove all non alphanumeric characters from a string in PHP?

This is the code, that I'm currently using:

$url = preg_replace('/\s+/', '', $string);

It only replaces blank spaces.

possible duplicate of [How do I remove non alphanumeric characters in a string? (including ß, Ê, etc.)](http://stackoverflow.com/questions/7271607/how-do-i-remove-non-alphanumeric-characters-in-a-string-including-ss-e-etc) — mario, Jul 04 '12 at 00:51
@mario: That's a bit different since it deals with Unicode. I'm sure a perfect duplicate exists tho... — Alix Axel, Jul 04 '12 at 00:57
possible duplicate of [Remove non-alphanumeric characters](http://stackoverflow.com/questions/659025/remove-non-alphanumeric-characters) — trejder, Jan 15 '15 at 13:04

John Conde · Accepted Answer · 2017-05-05T12:25:17.893

135

$url = preg_replace('/[^\da-z]/i', '', $string);

edited May 05 '17 at 12:25

answered Jul 04 '12 at 00:40

John Conde

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In case anyone else was momentarily confused by Xeoncross' comment at first glance, his point was that the answer *doesn't* support Unicode characters. But the solution in Xeoncross' link *does*. – orrd Sep 29 '16 at 04:57

score 20 · Answer 2 · answered Jul 04 '12 at 01:27

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At first take this is how I'd do it

$str = 'qwerty!@#$@#$^@#$Hello%#$';

$outcome = preg_replace("/[^a-zA-Z0-9]/", "", $str);

var_dump($outcome);
//string(11) "qwertyHello"

Hope this helps!

answered Jul 04 '12 at 01:27

sevenadrian

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score 14 · Answer 3 · answered Jul 30 '13 at 13:05

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Not sure why no-one else has suggested this, but this seems to be the simplest regex:

preg_replace("/\W|_/", "", $string)

You can see it in action here, too: http://phpfiddle.org/lite/code/0sg-314

answered Jul 30 '13 at 13:05

Chuck Le Butt

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The simplest and efficient at the same time is `preg_replace("/[\W_]+/", "", $string)`. – Wiktor Stribiżew Jun 26 '16 at 10:55

score 9 · Answer 4 · answered Jun 26 '17 at 07:31

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You can use,

$url = preg_replace('/[^\da-z]/i', '', $string);

You can use for unicode characters,

$url = preg_replace("/[^[:alnum:][:space:]]/u", '', $string);

answered Jun 26 '17 at 07:31

Damith Ruwan

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score 5 · Answer 5 · answered Jul 04 '12 at 00:42

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preg_replace('/[\s\W]+/', '', $string)

Seems to work, actually the example was in PHP documentation on preg_replace

answered Jul 04 '12 at 00:42

lisovaccaro

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Keep in mind that this will *keep* underscores as they are considered word characters and keeps spaces as well – John Conde Jul 04 '12 at 00:43
I didn't know about underscores, but it isn't keeping spaces. – lisovaccaro Jul 04 '12 at 02:08

score 3 · Answer 6 · answered Jul 04 '12 at 00:55

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$alpha = '0-9a-z'; // what to KEEP
$regex = sprintf('~[^%s]++~i', preg_quote($alpha, '~')); // case insensitive

$string = preg_replace($regex, '', $string);

answered Jul 04 '12 at 00:55

Alix Axel

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Remove all non-alphanumeric characters using preg_replace

6 Answers6