对ajax .post调用上的错误的空响应

Question

I'm doing an ajax call to delete an SQL entry. If the entry is found and deleted, I return HTTP Code 200 with the message, that the entry was deleted. So it jumps into the .done section and prints my message together with DONE . In the case, the entry is not found, I want to jump into the .fail section, so I return HTTP Code 400 with my message, that the entry wasn't found. It prints the ERROR , but the message is always empty. If I check the return of the ajax call in the console of chrome I see my message together with code 400.

$.post( 'ajax/project.php', data )
    .fail(function(res) {
        $( "#info" ).html("ERROR");
    })

    .done(function(res) {
        $( "#info" ).html("DONE");
    })

    .always(function(res) {
        $( "#debug" ).html(res);
    });

Any solution to throw an error to jump into .fail but with receiving my error message? I through the error like this:

function myError( $msg, $code=200, $die=true) {
    http_response_code($code);
    echo $msg;
    if($die)
        die();
}

My call of myError looks like this:

if(!$stmt->affected_rows)
    myError('Project #'.$pid.' not found', 400);

Edit2: As you can see in the screenshot below, with HTTP code 200 it just returns my message, in HTTP code 400 it returns my message in an object. Looks like I have to do a workaround to catch both possible returns, but I do not really understand why it acts different.

Edit1: Just found out, if I alert the result with alert(res); in the .always section I get [object Object] in the error-case instead of my message.

Answer 1

As you can see in this screenshot of the console of chrome, the server responses are different in case of success (200) and of error (400/500), but I don't know why..

However, this is a dirty hack, but it works for now.

$.post( 'ajax/project.php', data )
    .fail(function(res) {
        $( "#info" ).html("ERROR");
    })

    .done(function(res) {
        $( "#info" ).html("DONE");
    })

    .always(function(res) {
        console.log(res);
        if(res instanceof Object)
            $( "#debug" ).html(res.responseText);
        else
            $( "#debug" ).html(res);
    });

If anybody can give me a better example of how to solve this, I would be happy :)