private static function getRegex()
{
if (!self::$regex) {
$words = [''];
// empty word to merge immediate tokens
foreach (ElasticSearch::getStopwords() as $word) {
$words[] = preg_quote($word, '~');
}
self::$regex = '~' . preg_quote(self::END, '~') . '(\\W*\\s*(' . implode('|', $words) . ')\\s*\\W*)' . preg_quote(self::START, '~') . '~';
}
return self::$regex;
}
