Getting particular data from json_encode response - php

Question

I have a file ajax.php which I am using to process data passed through jquery. I have this particular line of code called on successful form verification:
$.post("/ajax.php",{'request': 'emailLogin', 'loginmail': mail, 'loginpass': pass}, function(data) {} );
data in my case is: {"valid":true}{"auth":false}which is returned as a response from ajax.php, but I can't seem to file the correct way of defining "auth" and a variable with value "false".
My ajax.php is just checking if login and password are in the database and than echo json_encode(array('auth' => false)); or echo json_encode(array('auth' => true)); depending on the result. But it has also contain these lines:
if( isset($_POST['loginmail'])) {
$usermail = htmlspecialchars($_POST['loginmail']);
if (!filter_var($usermail, FILTER_VALIDATE_EMAIL)) {
$response = array('valid' => false, 'message' => 'You did not enter a correct email address.');
} else {
// All good
$response = array('valid' => true);
}
}
echo json_encode($response);

Answer 1

Don't echo json_encode($response) separately from the authentication result, you need to combine them. After you do the authentication, do:
$response['auth'] = $result_of_authentication;
then do
echo json_encode($response);
Once you do this, you should be able to access data.auth in Javascript. You should tell $.post that it's returning JSON:
$.post("/ajax.php",{
'request': 'emailLogin',
'loginmail': mail,
'loginpass': pass},
function(data) {
alert(data.auth);
},
"json");

Answer 2

Based on your PHP code you should be able to access the valid attribute like so:
$.post("/ajax.php",{'request': 'emailLogin', 'loginmail': mail, 'loginpass': pass}, function(data) {
var auth = data.valid;
if (auth) {
// do something!
} else {
// do something else!
}
});
Also there is a bug in your PHP code, you need to set up a default value for $response like so:
$response = array('valid' => false, 'message' => 'Email address is required');
if( isset($_POST['loginmail'])) {
$usermail = htmlspecialchars($_POST['loginmail']);
if (!filter_var($usermail, FILTER_VALIDATE_EMAIL)) {
$response = array('valid' => false, 'message' => 'You did not enter a correct email address.');
} else {
// All good
$response = array('valid' => true);
}
}
echo json_encode($response);
Otherwise if $_POST['loginmail'] is not set your app with throw an undefined variable exception
EDIT:
As Barmar pointed out in his answer, you should only echo a response back once time to avoid creating an invalid response. Any data you need should be sent back in a single array. I don't see you doing that in your PHP code but you do make mention of echoing another array ['auth' => false] which will not work the way you want it to