PHP preg_replace() compilation failed: missing )

Question

Hello, I have the following function to return a clean path for a script.

function cleanPath($path) {
     $path = (string) $path;
     $path = preg_replace(
      array(
      '#[\n\r\t\0]*#im',
      '#/(\.){1,}/#i',
      '#(\.){2,}#i',
      '#(\.){2,}#i',
      '#('.DIRECTORY_SEPARATOR.'){2,}#i'
      ),
      array(
      '',
      '',
      '',
      '/'
      ),
      $path
      )
     ;
     return rtrim($path,DIRECTORY_SEPARATOR);
    }

PHP gives the error:

Warning: preg_replace() [function.preg-replace]: Compilation failed: missing ) at offset 7 in C:\wamp\www\extlogin\app\ni\inc\classes\cfiletree.php on line 18

Any ideas about what's wrong and how to fix it?

Thank you.

Answer 1

Most likely DIRECTORY_SEPARATOR is \ which means it'll escape the ) rather than match a backslash. You need to escape DIRECTORY_SEPARATOR so that it becomes \\ in the regex.

The safest way to escape strings placed in regular expressions is to use preg_quote:

preg_quote(DIRECTORY_SEPARATOR, '#');

The second argument, '#', is the separator you use for your regular expression, which in your case is #.