get uploaded file, accept only PDF extension, give random file name and store to folder

function upload_file($file, $folder, $allowed_ext){
    $ext = end(explode(".", $file['name']));
    $tmp_name = $file['tmp_name'];
    $new_name = uniqid().".".$ext;
    $new_location = "uploads/".$folder."/".$new_name;
    if($ext == $allowed_ext){
        move_uploaded_file($tmp_name, $new_location);
        return $new_location;
    }else{
        return false;
    }
}

upload_file($_FILES['file'], 'documents', 'pdf');