Is it really required to escape backslashes in regex patterns?

Question

This might be a dumb question, but I have trouble understanding why the following code works as expected

$text = "ab    cd";
$text = preg_replace("/\s+/", "", $text);
echo $text;

and outputs abcd.

Shouldn't the backslash in \s be escaped to get its literal meaning inside the regular expression?

Jon · Accepted Answer · 2013-08-08 15:11:58Z

4

Not necessarily, because the string literal rules say that if \ is followed by anything other than another \ or a ' it is treated as any other character. This general rule also affects double-quoted strings, although in that case there are more recognized escape sequences than just these two.

You could escape it if you wanted to, but personally I think the world has enough backslashes already.

answered Aug 8, 2013 at 15:11

Jon

439k85 gold badges756 silver badges820 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Spudley Over a year ago

+1. It gets really confusing when you realise that even some characters that would be picked up by PHP as escape sequences don't need to be double-escaped because the escaped character is valid inside the regex. So you can get away with \n, or you can escape it \\n. But where it really gets bad is when you have an actual backslash in your string to search for. Try matching a Windows network path (`\\nas\folder\etc`) or a find escaped characters in a JSON string, and you'll end up with a monstrous cascade of backslashes. Fun fun fun.

Collectives™ on Stack Overflow

Is it really required to escape backslashes in regex patterns?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related