Wie importiere / lade ich Dateien mit jQuery AJAX hoch?

Ich stoßeimmer wieder aufein Problembeim Abrufen der Datei (en)in AJAX,damit die Server-Ajax-Funktion die Daten verarbeiten kann. Wie kannich dafür sorgen,dass $ _FILES wiebei der Standardaktion (in Formularelementeintegriert) übergeben wird?

HTML-Formular

 <form id="frmImport" name="frmImport" method="post" enctype="multipart/form-data" >
    <input id="file_import" name="importData" type="file" />
    <br/>
    <button id="btn_import" type="submit" >Import</button>
</form>
 

JavaScript

     jQuery(document).ready(function($) {
    //This is already setup and sent from the server side, and is
    // is used to prevent unauthorized users from uploading data.
    var importnonce = "3x4mpl3f4k3n0nc3"; 

    $('#frmImport').submit(function(e) {
        e.preventDefault();

        // CHECK FOR ANY ERRORS HERE.
        // IF ERRORS EXIST, RETURN FALSE TO END OPERATIONS.

        var formData = new FormData();
        formData.append('action', 'ajax_handler_import');
        formData.append('_ajax_nonce', importNonce);

        // Issue occures here. PHP gets a string '[object FormData]'.
        var importFiles = $('#file_import')[0].files;
        formData.append('uploadFiles', importFiles);

        jQuery.ajax({
            url: ajaxurl,
            type: 'POST',
            cache: false,
            contentType: false,
            processData: false,

            data: formData,

            beforeSend: function(jqXHR, settings) {
                console.log("Haven't entered server side yet.");
            },
            dataFilter: function(data, type) {
                // Used to parse data, and possibly check for errors.
                console.log("JSON string echoed back from server side.");
            },
            success: function(data, textStatus, jqXHR) {
                console.log("Back from server-side!");
                // Checking errors that may have been caught on the server side that
                // normally wouldn't display in the error Ajax function.
                if (data.msg != 'success') {
                    alert(data.error);
                }
            },
            error: function(jqXHR, textStatus, errorThrown) {
                console.log("A JS error has occurred.");
            },
            complete: function(jqXHR, textStatus) {
                console.log("Ajax is finished.");
            }
        });

        return false;
    });
});
 

PHP Server/Handler

 <?php
class server {
    function ajax_import_handler() {
        check_ajax_referer("ajax_handler_import");

        $rtnData = new stdClass();
        $rtnData->msg = 'success'; //For signifying Server errors
        $rtnData->error = ''; //For displaying custom error messages or using the try/catch method

        //Do Stuff
        foreach ($_FILES as $key => $value) {
            //GET FILE CONTENT
            $file_array[$key] = json_decode(file_get_contents($value['tmp_name']));
        }

        // Do more stuff with file(s).

        // Add stuff to $rtnData.

        echo json_encode($rtnData);
    }
}
?>
 

I keep running into an issue getting the file(s) added in AJAX so that the server ajax function can process the data. How can I get the $_FILES to be passed the same as with the default action (built into form elements)?

HTML Form

<form id="frmImport" name="frmImport" method="post" enctype="multipart/form-data" >
    <input id="file_import" name="importData" type="file" />
    <br/>
    <button id="btn_import" type="submit" >Import</button>
</form>

JavaScript

    jQuery(document).ready(function($) {
    //This is already setup and sent from the server side, and is
    // is used to prevent unauthorized users from uploading data.
    var importnonce = "3x4mpl3f4k3n0nc3"; 

    $('#frmImport').submit(function(e) {
        e.preventDefault();

        // CHECK FOR ANY ERRORS HERE.
        // IF ERRORS EXIST, RETURN FALSE TO END OPERATIONS.

        var formData = new FormData();
        formData.append('action', 'ajax_handler_import');
        formData.append('_ajax_nonce', importNonce);

        // Issue occures here. PHP gets a string '[object FormData]'.
        var importFiles = $('#file_import')[0].files;
        formData.append('uploadFiles', importFiles);

        jQuery.ajax({
            url: ajaxurl,
            type: 'POST',
            cache: false,
            contentType: false,
            processData: false,

            data: formData,

            beforeSend: function(jqXHR, settings) {
                console.log("Haven't entered server side yet.");
            },
            dataFilter: function(data, type) {
                // Used to parse data, and possibly check for errors.
                console.log("JSON string echoed back from server side.");
            },
            success: function(data, textStatus, jqXHR) {
                console.log("Back from server-side!");
                // Checking errors that may have been caught on the server side that
                // normally wouldn't display in the error Ajax function.
                if (data.msg != 'success') {
                    alert(data.error);
                }
            },
            error: function(jqXHR, textStatus, errorThrown) {
                console.log("A JS error has occurred.");
            },
            complete: function(jqXHR, textStatus) {
                console.log("Ajax is finished.");
            }
        });

        return false;
    });
});

PHP Server/Handler

<?php
class server {
    function ajax_import_handler() {
        check_ajax_referer("ajax_handler_import");

        $rtnData = new stdClass();
        $rtnData->msg = 'success'; //For signifying Server errors
        $rtnData->error = ''; //For displaying custom error messages or using the try/catch method

        //Do Stuff
        foreach ($_FILES as $key => $value) {
            //GET FILE CONTENT
            $file_array[$key] = json_decode(file_get_contents($value['tmp_name']));
        }

        // Do more stuff with file(s).

        // Add stuff to $rtnData.

        echo json_encode($rtnData);
    }
}
?>