我想加载带有消息的php以在提交后隐藏表单但是event.preventDefault（）; 破坏我的.php文件中的“已存在”检查

After submitting there must exist 3 possible states:

1. Data saved and php message is loaded onto where the form was.
2. Data already exists and I load a different php informing the user.
3. An error occurred, show an alert asking the user to please try again.

This is what my submit .php looks like:

$test="select * from launchpage where email_launchPage ='$email'";
$testing=$link->query($test);
$alreadyExists=$testing->num_rows;

if($alreadyExists ==1){
    echo "<script>alert('already exists');window.history.go(-1);</script>";
} else{
    $sqlInsertListingType="insert into launchpage(email_launchPage,language_launchPage) values('".$email."','".$language."')";
    $link->query($sqlInsertListingType);
    echo "<script>alert('saved');window.history.go(-1);</script>";
}

It works fine on it's own and this is my try at an ajax request to submit:

$(document).on("submit","#form",function(event){
    event.preventDefault();
    var formURL = $(this).attr("action");
    var formType = $(this).attr("method");
    var formData = $(this).serialize();
    $.ajax({
        url: formURL,
        type: formType,
        data: formData,
        success:function(data, textStatus, jqXHR){
            console.log('went through ajax');
        },
        error: function(jqXHR, textStatus, errorThrown){
            console.log("i've ruined something");
        }
    });
});

Which also works, but because of the .preventDefault(); I "don't" know if the data was saved or not.

I have no idea what I should try to do to bring these 2 together, or if there's a better way to do this...

I'm guessing this must be rather easy to solve, I'm just missing something I haven't learned yet.

Don't return JS or other html. return some json:

<?php

... process form data
if (processing succeeds) {
   $msg = array(
       'code' = 1,
       'message' = 'Success'
   );
} else {
   $msg = array(
       'code' => 0,
       'message' => 'Failed, something dun blowned up'
   );
}
echo json_encode($msg);

Then in your success handler:

success: function(data) {
        if (data.code == 1) {
             do_success_stuff();
        } else {
            alert('requested failed with error #' + data.code + " and message '" + data.message + "'");
        }
 }