Fix regex

Author: nikic

lib/PhpParser/Lexer/Emulative.php

@@ -67,15 +67,15 @@ protected function requiresEmulation($code) {
             return false;
         }
 
-        if (preg_match('/\?\?|<=>|yield[ \n\r\t]+from/', $code)) {
+        if (preg_match('(\?\?|<=>|yield[ \n\r\t]+from)', $code)) {
             return true;
         }
 
         if (version_compare(PHP_VERSION, self::PHP_5_6, '>=')) {
             return false;
         }
 
-        return preg_match('/\.\.\.|(?<!/)\*\*(?!/)/', $code);
+        return preg_match('(\.\.\.|(?<!/)\*\*(?!/))', $code);
     }
 
     /*