PHP

laravel belongsto many create

/**
 * Insert the signature
 *
 * @param Request $request
 * @return ...
 */
 public function store( Request $request ) {
    // your validation

    $signature->users()->attach( $request->input('user_id') );

    // return
}

laravel belongsto many create

/**
 * Update the signature with the particular id
 *
 * @param $id
 * @param Request $request
 * @return ...
 */
 public function update( $id, Request $request ) {
    // your validation

    $signature->users()->sync( $request->input('user_id') );

    // return
}