preg_match() Unknown modifier '[' help

Question

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: 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.

Answer 2

If you don't like delimiters: use T-Regx library, which works exactly like preg_match() but doesn't need delimiters.

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

//         ^ no delimiters :)                                          ^

and just use this

$match = pattern($pattern)->match($str)->first();

this results in

string(11) "NRHVzbJVx8I"