文件上传单击提交按钮以获取此错误500内部服务器

Question

if(isset($_POST['submit'])) {

    $tmp_file = $_FILES['file_upload']['tmp_name'];
    $target_file = basename($_FILES['file_upload']['name']);
    $upload_dir = "images/software-logo/window";
    $upload_db = "images/software-logo/window";

if(move_uploaded_file($tmp_file, $upload_dir."/".$target_file)) {
    $ins_qury = mysql_query("UPDATE `table` SET `col1` ='$upload_db/$target_file' WHERE `col2` = $update_logo_id");

    $message = "File uploaded successfully.";
        } else {
            $error = $_FILES['file_upload']['error'];
        $message = $upload_errors[$error];
    }           
}