Script is not fetching data from php to ajax script after success - php

Question

I don't really understand why this does not work - I have read a whole lot about this specific problem, but I must be missing something.
I want to alert the "echo" from the PHP - which it doesn't.
AJAX:
$("#SaveChangesEmail").click(function() {
var newemail = $("#mynewemail").val();
$.ajax({
type: "POST",
url: "checkemail.php",
data: {newemail:newemail},
datatype: "json",
success: function(data){
alert(data);
}
});
});
PHP (checkemail.php)
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
if($email == $row['myemail']){
echo "This is your current email";
}
else if($email != $row['myemail']){
$results = $con->query("
UPDATE members SET
myemail='".$email."'
WHERE m_id = '".$m_id."'") or die(mysqli_error($con));
echo "Your email is changed";
}
} else {
echo "Please provide a correct email";
}
The database is updating, do the script itself runs perfectly, but after the "success" - it doesn't alert anything.
UPDATE
I have now tried this:
AJAX:
$("#SaveChangesEmail").click(function() {
var newemail = $("#mynewemail").val();
$.ajax({
type: "POST",
url: "checkemail.php",
data: {newemail:newemail},
datatype: "text",
success: function(data){
if(data == 1) {
alert("This is your current email");
}
else if(data == 2) {
alert("Your email is changed");
}
else if(data == 3) {
alert("Please provide a correct email");
}
}
});
});
PHP (checkemail.php)
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
if($email == $row['myemail']){
echo "1";
}
else if($email != $row['myemail']){
$results = $con->query("
UPDATE members SET
myemail='".$email."'
WHERE m_id = '".$m_id."'") or die(mysqli_error($con));
echo "2";
}
} else {
echo "3";
}
The console is returning the raw data (1,2,3) but the alert is still not showing!