PHP Regex reduce a repeated character to a single instance

Question

I want to rid a text for repeated exclamation marks (!!!), question marks (??) or full stops (....) and replace them with a single instance of themselves. So I need "one preg_replace to rule them all" basically.

I currently have three separate patterns being executed:

preg_replace("/[!]{2,}/","!", $str);
preg_replace("/[?]{2,}/","?", $str);
preg_replace("/[.]{2,}/",".", $str);

Is there a way to replace the found character with a single instance of itself using just one regex pattern?

I need to turn:

Ok!!!
Really????
I guess.....

into:

Ok!
Really?
I guess.

With one regex pattern.

Wiktor Stribiżew · Accepted Answer · 2017-08-28 06:53:49Z

11

Use a capturing group with a backreference:

([?!.])\1+

Replace with $1.

See the regex demo.

Details

([?!.]) - matches and captures into Group 1 a single char: ?, ! or .
\1+ - matches one or more instances of the content captured into Group 1.

PHP demo:

$str = "Ok!!!\nReally????\nI guess.....";
$res = preg_replace('/([?!.])\1+/', '$1', $str);
echo $res;

Results:

Ok!
Really?
I guess.

answered Aug 28, 2017 at 6:53

Wiktor Stribiżew

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3 Comments

Hasen Over a year ago

That works great, thanks! For ages it wouldn't work for me but I found it only works with single quotes in the code? With double quotes the pattern didn't match for some reason. Anyway, its great.

Wiktor Stribiżew Over a year ago

@Hasen: See the Backreference does not work in PHP. Inside double quotes, you need to double the backslashes.

Hasen Over a year ago

Oh I see...interesting.

Hasen · Accepted Answer · 2017-08-28 07:28:25Z

-1

Just for completion, I thought I'd post my own answer based on my original code after viewing the answer given by another.

 pattern ([!?.]){2,}

 preg_replace('/([!?.]){2,}/','$1', $str);

This pattern also seems to work fine.

answered Aug 28, 2017 at 7:28

Hasen

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1 Comment

Toto Over a year ago

Be carefull, that doesn't do the same thing than other answer. This will replace .!!.?? with . but may be is that what you want.

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