Open Subs.php and alter the following things.
After:
static $bbc_codes = array(), $itemcodes = array(), $no_autolink_tags = array();
static $disabled;
Add:
$message = preg_replace('/http:\/\/([^\s\.]+).(youtube.com\/watch\?v=)([A-Za-z0-9\-]+)([^\s]*)/', '[youtube]$3[/youtube]', $message);
After:
array(
'tag' => 'b',
'before' => '<b>',
'after' => '</b>',
)
Add:
array(
'tag' => 'youtube',
'before' => ''
),
