Regex search in phpStorm does not work

Hello,
Can anybody give me a hint why regex search

$redirect_url[\s]+=

does not work in my case ?
http://imgur.com/a/3ZvAC


for code line :

$redirect_url = $this->backend_home_url . '/admin/product/index?' . $page_parameters_with_sort;

If to change regex to
$redirect_url =
it works ok.

Thanks!