your 'data' field is an Array
url: "login.php",
data: {"email": email, "password": password},
success: function(response) {
to get values in :
$_POST[0][0] ;
$_POST[0][1] ;
/or, as it's an associative Array ;
$_POST[0]["email"] ; // email
$_POST[0]["password] ; // password
the data field is at index = 0 : $_POST[0]