PHP preg_match_all doesn't match an escaped quote

Question

This code:

<?php
    $string = "\"single quote";
    preg_match_all("/\"/im", $string, $m);
    $all_quotes = count($m);
    preg_match_all("/\\\"/im", $string, $m);
    $escaped_quotes = count($m);

    echo "<pre>";
     echo "<b>string:</b> $string<br>";
     echo "<b>all quotes:</b> $all_quotes<br>";
     echo "<b>escaped quotes:</b> $escaped_quotes<br>";
    echo "</pre>";
?>

Is supposed to match all quotes, then match all escapes quotes, and echo the results. For some reason, for string "single quote it echoes both one quote and one escaped quote, however the pattern /\\\"/im matches nothing when executed in http://regexr.com with same string.

The `"\""` does not contain a backslash. Check [this demo to see how to declare a backslash in a PHP string literal](http://ideone.com/c2In3Z). — Wiktor Stribiżew, Jan 12 '17 at 20:53
Possible duplicate of [Right way to escape backslash \[ \ \] in PHP regex?](http://stackoverflow.com/questions/11044136/right-way-to-escape-backslash-in-php-regex) — 4castle, Jan 12 '17 at 21:15

Elon Than · Accepted Answer · 2017-01-12T20:55:15.760

0

Edited:

Ok, so first of all, you are getting count from preg_match_all as return value. The way you are doing it now will always show you 1 because preg_match_all returns array (with one element in your case).

As Wiktor Stribiżew stated, you need to adjust your regex too

preg_match_all("/\\\\\"/im", $string, $m);

I'm not 100% sure that I understand your question but I'll try to answer it.

You are probably expecting to see \" in your $string variable, right?

But that's not the case. PHP will remove that backslash before saving your string. It's only hint for PHP that you want to get literal " and that you are not trying to end string here.

In case you want (for any reason) get \" , you have to use code like this:

$string = "\\\"single quote";

edited Jan 12 '17 at 20:55

answered Jan 12 '17 at 20:34

Elon Than

9,603
4
27
37

No, the $string is perfectly fine and should be `"single quote` – user7401478 Jan 12 '17 at 20:35
@WearyAdventurer so what do you expect from that code? Should it show one quote and zero escaped quotes? – Elon Than Jan 12 '17 at 20:37
Yes, 1 quote and 0 escaped quotes. – user7401478 Jan 12 '17 at 20:38
@WearyAdventurer updated – Elon Than Jan 12 '17 at 20:45
1

Problem solved. Thanks! – user7401478 Jan 12 '17 at 20:47
1

*You regex is fine* is not true. `preg_match_all("/\\\"/im", $string, $m);` matches unescaped quotes because `"\\\""` is actually ``\"`` pattern that matches a `"`. – Wiktor Stribiżew Jan 12 '17 at 20:48
@WiktorStribiżew it is fine for OPs task. He wants to match literal `\"` string. – Elon Than Jan 12 '17 at 20:49
1

To match a quote, one needs `preg_match_all("/\"/im", $string, $m);`. If the string is `\"`, then the `preg_match_all("/\\\"/im", $string, $m);` will only match `"`, and not ``\"``. – Wiktor Stribiżew Jan 12 '17 at 20:50
@WiktorStribiżew point for you. Two more backslashes. – Elon Than Jan 12 '17 at 20:54

PHP preg_match_all doesn't match an escaped quote

1 Answers1