PHP preg_match escaping character

Question

So I'm having the following issue with regular expressions:

What I am trying to achieve: Get the last element of the namespace, in this case "BAZ"

To do so I am using the regular expression below:

preg_match("/[^\\]*$/", 'Foo\Bar\Baz', $output);

For some reason I get this error:

preg_match(): Compilation failed: missing terminating ] for character class at offset 6

You don't need a regex for this, `echo end(explode('\\', 'Foo\Bar\Baz'));`. — chris85, Mar 21 '16 at 18:36
Agreed .... RegEx should be the last option ..! @chris85 write an answer, I will give you +1 `;-)` — Shafizadeh, Mar 21 '16 at 18:37

anubhava · Accepted Answer · 2016-03-21T18:28:08.010

3

You need to double escape \\ because in PHP regex is entered as string where which requires each literal \ as \\ and regex engine needs additional escaping of each \ so you end up with 4 \:

preg_match('/[^\\\\]*$/', 'Foo\Bar\Baz', $output);

edited Mar 21 '16 at 18:28

answered Mar 21 '16 at 18:24

anubhava

713,503
59
514
593

2

[Demo](https://3v4l.org/bIOi8) – Shafizadeh Mar 21 '16 at 18:26
Yes I just added some explanation of escaping – anubhava Mar 21 '16 at 18:28
Odd .. [**three** back-slash works too](https://3v4l.org/KWcjX) – Shafizadeh Mar 21 '16 at 18:29
@Shafizadeh http://stackoverflow.com/questions/28062568/why-3-backslash-equal-4-backslash-in-php – chris85 Mar 21 '16 at 18:33
Yes I know 3 `\\\` work as well in PHP but it is recommended to use 4 `\\\\` – anubhava Mar 21 '16 at 18:34

PHP preg_match escaping character

1 Answers1