ZipArchive not creating file

ZipArchive not creating file

if(isset($_POST['submit'])){
if(!empty($_FILES['files']['name'])){
$Zip = new ZipArchive();
$Zip->open('uploads.zip', ZIPARCHIVE::CREATE);
$UploadFolder = "uploads/";
foreach($_FILES['files'] as $file){
$Zip->addFile($UploadFolder.$file);
}
$Zip->close();
}
else {
echo "no files selected";
}
}
What is wrong here ? I have just watched a tutorial of creating archives
and adding files in it but it is not working ...I am using php 5.4 . It is
not even giving me any error. Can any one please guide me what i am doing
wrong here.
Below is the form
<form action="" method="POST" enctype="multipart/form-data">
<label>Select files to upload</label>
<input type="file" name="files">
<input type="submit" name="submit" value="Add to archieve">
</form>