php - is_uploaded_file にはエラーが表示されますが、エラー コードは返されません

Question

次のコードがあります。

 if (!is_uploaded_file($_FILES['sb_file']['tmp_name']))
                           {
                               echo "Error in Uploading File <br>".$_FILES["sb_file"]["error"][$count];
                           }

is_uploaded_file$_FILES['sb_file']['errors'] でさえ false を返します 0 を返しますが、ファイルは宛先フォルダーに移動していません。エラーを追跡するにはどうすればよいですか?

foreach ($_FILES['sb_file']['name'] as $filename)
        {
            //make sure no empty thing goes
            if($filename!=""&&$filename!=null)
            {
                $temp = explode(".", $filename);
                $extension = end($temp);
                $upload_folder = "/home/content/w/k/1/wk1989/html/".trim($config["UPLOAD_FOLDER"]);
                 if(!(in_array($extension, $allowedExts)))
                    print "$filename has Invalid file Type <br />";
                 else
                 {
                     $uploaded_file_name = $filename."-".date("YmdHis").".".$extension;
                     if ($_FILES["sb_file"]["error"][$count] > 0)
                        {
                            echo "<br />Error: " . $_FILES["sb_file"]["error"][$count] . "<br />";
                        }
                        else
                        {
                            $target_path = "uploads/";
                            $target_path = $target_path.basename( $file_upload['name']); 
                            print "Path = $target_path <br>";
//                            if(move_uploaded_file($file_upload['tmp_name'], $target_path)) {
//                            //    echo "The file ".  basename( $file_upload['name']). " has been uploaded";
//                            } else{
//                                //echo "There was an error uploading the file, please try again!";
//                            }
                           move_uploaded_file($_FILES["sb_file"]["tmp_name"][$count],$upload_folder.$uploaded_file_name);
//                           if (!is_uploaded_file($_FILES['sb_file']['tmp_name'][$count]))
//                           {
//                               echo "Error in Uploading File <br>".$_FILES["sb_file"]["error"][$count];
//                           }
//                           else
//                           {
//                               
//                           }
                           $is_upload = true;
                           echo "Uploaded = ".$upload_folder.$uploaded_file_name;

                        }
                        if($is_upload)
                        {
                            $uploaded_files[] = $upload_folder.$uploaded_file_name;
                        }
                 } 
            }
             $count++;
        }