Jquery ajax returning 404 not found

I’m using Ajax to pass my form data and files to a PHP file for processing.

Javascript:

$("form#applyform").submit(function(){

var data = new FormData();
jQuery.each($('#file')[0].files, function(i, file) {
    data.append('file-'+i, file);
});

$.ajax({
    url: 'ValidateApplication.php',
    data: data,
    cache: false,
    contentType: false,
    processData: false,
    type: 'POST',
    success: function(data){
        alert(data);
    }
});

}

ValidateApplication.php definitely exists. I can view it if I type in the address into the web browser, however when I submit the form chrome console returns 404.

The PHP is in the same folder as the HTML page the JavaScript is running on so I am confused as to why I keep getting a 404.

UPDATE

Changing POST to GET gets rid of the 404 error, but returns a 500 Internal Server Error

UPDATE 2

Changing the action of the form to =”ValidateApplication.php” and submitting it as normal (without AJAX) leads to the correct file without any errors.

Answer

It seemed to be a problem with the FormData object. Once I changed my method to use .serialize() instead, the page worked just fine.

$("form#applyform").submit(function(){

    var data = $("form#applyform").serialize();
    jQuery.each($('#file')[0].files, function(i, file) {
        data.append('file-'+i, file);
    });

    $.ajax({
        url: 'ValidateApplication.php',
        data: data,
        cache: false,
        contentType: false,
        processData: false,
        type: 'POST',
        success: function(data){
            alert(data);
        }
    });
}