Regex Binary Pattern Search in PHP

Question

I am trying to find and replace binary values in strings:

$str = '('.chr(0x00).chr(0x91).')' ;
$str = preg_replace("/\x00\x09/",'-',$str) ;

But I am getting "Warning: preg_replace(): Null byte in regex" error message.

How to work on binary values in Regex/PHP?

Answer 1

It is because you are using double quotes " around your regex pattern, which make the php engine parse the chars \x00 and \x09.

If you use single quotes instead, it will work:

$str = '(' . chr(0x00) . chr(0x91) . ')' ;
$str = preg_replace('/\x00\x09/', '-', $str) ;

But your regex seems also not to be correct, if I understood your question correctly. If you want to replace the chars \x00 and \x91 with a dash -, you must put them into brackets []:

$str = preg_replace('/[\x00\x91]/', '-', $str) ;