Keep only a-z and underscore characters

Question

How do I strip all characters from a string, besides a-z (with uppercase) and the underscore _ ?

possible duplicate of [Removing spaces and anything that is not alphanumeric](http://stackoverflow.com/questions/4210419/removing-spaces-and-anything-that-is-not-alphanumeric) — Niet the Dark Absol, Mar 28 '12 at 11:16

Niko · Accepted Answer · 2012-03-28T11:23:03.180

8

How about a regular expression?

$output = preg_replace('#[^a-zA-Z_]#', '', $input);

This replaces everything that matches the expression with an empty string.

[] is a group of symbols, the ^ at the beginning of the group means: this group contains every character that is NOT mentioned afterwards. So it contains everything that is not a-z or A-Z or the underscore.

edited Mar 28 '12 at 11:23

answered Mar 28 '12 at 11:17

Niko

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score 1 · Answer 2 · answered Mar 28 '12 at 11:17

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Read more about regular expressions. Try this

$string = preg_replace('/[^a-z_]/', '', $string);

answered Mar 28 '12 at 11:17

safarov

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score 1 · Answer 3 · answered Mar 28 '12 at 11:18

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You can use the preg_replace function for this:

$string = 'Text& with* ch@racters that get# removed, but_not_underscore.';
echo preg_replace( '/[^A-Za-z_]/', '', $string );

answered Mar 28 '12 at 11:18

Tom

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Keep only a-z and underscore characters

3 Answers3