private function validate( $values ) {

		$is_valid = TRUE;

		foreach ( $values as $key => $value ) {

			if ( ! is_scalar( $value ) ) {
				continue;
			}

			foreach ( $this->validators as $validator ) {
				$is_valid = $validator->is_valid( $value );

				if ( ! $is_valid ) {
					$this->error_messages[ $key ] = $validator->get_error_messages();
					break;
				}
			}

			if ( ! $is_valid ) {
				break;
			}
		}

		return $is_valid;
	}