Yes there are ways to check if the login is successful but you need to return an object back from the php script or an array that will have the message to print perhaps, the status of the attempt etc. (if you want to do it properly)

You cannot do just echo php objects but you can output strings. So you need to serialize the results from the php script in some way and send them back to the client. Some people use json for this I prefer to use just serialization more compatible.

So if your php result is an array
$result = array(
'status' => $login_status,
'message' => $message,
);

$output = serialize($result);
echo $output;

Then you need to reverse the results, there are jquery serialize/unserialize plugins you could use.

[code.google.com...]

Then you convert the results into a js array or object and you have pretty much everything to process on the client's end.

Or you can use json which does a similar thing, or you can do the quick and dirty way where you could echo just a specific string like 0 or 1, from the php that signifies whether the login was successful. But the code won't be too reusable.

$.post('/register/process.php', $("#myform").serialize(), function(data) { 

$('#results').html(data); 
if (data == "Success") {
  // Close the window
  window.close()
}
});