How to escape a slash character in the preg_match pattern?

Question

I have a text like this:

line 1/1/1/2

The text after the line phrase is the parameter of a function, for example when I call extractData('1/1/1/2' , 'The main text'):

function extractData($line, $text)
{
    $pattern = "/line(\s+)$line/";
    if(preg_match($pattern, $text)) {
        // some code
    }

}

How can I escape the slash character in the pattern? In other words, how should I write the pattern? ($pattern = "/line(\s+)$line/";)

hsz · Accepted Answer · 2014-08-12T12:01:48.213

12

You can use preg_quote function:

$pattern = '/line(\s+)' . preg_quote($line, '/') . '/';

edited Aug 12 '14 at 12:01

answered Aug 12 '14 at 11:51

hsz

Warning: preg_match(): Unknown modifier '1' in .... When I echo the pattern, it will be: /line(\s+)1/1/1/1/ – Aug 12 '14 at 12:00
@DiariB look at the documentation of `preg_quote` that hsz provided a link to. – faintsignal Aug 12 '14 at 12:01
@DiariB Sorry, I've edited my answer - delimiter missing. – hsz Aug 12 '14 at 12:02
@hsz It's a magic function, thanks :) – Aug 12 '14 at 12:04

score 5 · Answer 2 · answered Aug 12 '14 at 11:53

5

To scape any character you use \, so to escape / you use \/

If you want to escape \, you need to escape it as \\\

answered Aug 12 '14 at 11:53

The slash is in a variable and can't add any character to it – Aug 12 '14 at 11:55
Then go with `preg_quote` function as mentioned by hsz – Aug 12 '14 at 11:56

hwnd · Answer 3 · 2014-08-12T14:43:47.817

5

\Q and \E can be used to ignore regular expression metacharacters in the pattern as well.

$pattern = '~line(\s+)\Q' . $line . '\E~';

edited Aug 12 '14 at 14:43

answered Aug 12 '14 at 12:39

hwnd

That's good to know! Still something new here :) Didn't find much [documentation](http://perldoc.perl.org/perlre.html) about it, but seems [to work](http://regex101.com/r/pI4xW2/1). – Jonny 5 Aug 12 '14 at 12:51
1

@Jonny5 [perldoc](http://perldoc.perl.org/functions/quotemeta.html), [regex-info](http://www.regular-expressions.info/characters.html) – hwnd Aug 12 '14 at 13:45

3 Answers3