Your Localhost cannot process this request yet - HTTP ERROR 500

When syntax a PHP file, it gives an error 500. I can't fix it and I don't understand the reason for this error. Help me fix who understands, please.

<? php
$ login = trim ($ _ POST ['login']);
$ pass = trim ($ _ POST ['pass']);
$ pass = md5 ($ pass. "ghisfksdf12231");

$ mysql = new mysqli ("localhost", "root", "root", "velo-db");

$ result = $ mysql-> query ("SELECT * FROM` users` WHERE `login` = '$ login' AND` pass` = '$ pass' ");
$ user = $ result-> fetch_assoc ();
if (count ($ user) == 0) {
echo "No such user found"
exit ();
}

setcookie ('user', $ user ['name'], time () + 3600, "/");

$ mysql-> close ();
header ('Location: /')
?>