Ajax使用lighttpd将文件上传到php

Question

I have this script javascript:

function submitCID(){
    var file_data = $('#cidLoader').prop('files')[0];   
    var form_data = new FormData();                  
    form_data.append('cidLoader', file_data);

    $.ajax({
        url: "/uploadCid.php",
        dataType: 'text',
        cache: false,
        contentType: false,
        processData: false,
        data: form_data,    
        success: function(){
            alert("ok");
        },
        error: function(jqXHR, textStatus, errorThrown){
            alert(jqXHR.responseText);
        }
    });
}

to upload a .cid file (like xml).

PHP code is:

<?php
    $filename = $_FILES["cidLoader"]["name"];

    echo "Upload: " . $_FILES["cidLoader"]["name"] . "<br>";
    echo "Type: " . $_FILES["cidLoader"]["type"] . "<br>";
    echo "Size: " . ($_FILES["cidLoader"]["size"] / 1024) . " kB<br>";
    echo "Temp file: " . $_FILES["cidLoader"]["tmp_name"] . "<br>";
?>

And HTML form is like this:

<form method="POST" id="fileInfo" enctype="multipart/form-data">
    <input id="cidLoader" name="cidLoader" type="file" accept=".cid,.CID" />
</form>

Unfortunelly I get error: Undefined index: cidLoader

What is wrong?