preg_match() Unknown modifier '[' help

Question

Hi, I have this regex for getting the YouTube video ID:

(?<=v=)[a-zA-Z0-9-]+(?=&)|(?<=[0-9]/)[^&\n]+|(?<=v=)[^&\n]+

I get it from there: http://stackoverflow.com/questions/2597080/regex-to-parse-youtube-yid

The problem is I get preg_match() Unknown modifier '[' warning.

I know I have to enclose the regex delimiters but I have no idea how to do this.

Any help?

Answer 1

Try the following:

<?php
  $str = "http://www.youtube.com/ytscreeningroom?v=NRHVzbJVx8I";
  $pattern = '#(?<=v=)[a-zA-Z0-9-]+(?=&)|(?<=[0-9]/)[^&\n]+|(?<=v=)[^&\n]+#';
  preg_match($pattern, $str, $matches); 
  print_r($matches);
?>

Note, I'm using # as a delimiter here simply because the regular expression above contains forward slashes and escaping them makes the expression more difficult to read. This cleans it up by just a few pixels.