Question_Query::get_ids()

	public function get_ids() {
		if ( $this->ap_ids ) {
			return;
		}

		$this->ap_ids = array(
			'post_ids'   => array(),
			'attach_ids' => array(),
			'user_ids'   => array(),
		);

		foreach ( (array) $this->posts as $_post ) {
			$this->ap_ids['post_ids'][] = $_post->ID;
			$this->ap_ids['attach_ids'] = array_merge( explode( ',', $_post->attach ), $this->ap_ids['attach_ids'] );
			if ( ! empty( $_post->post_author ) ) {
				$this->ap_ids['user_ids'][] = $_post->post_author;
			}

			// Add activities user_id to array.
			if ( ! empty( $_post->activities ) && ! empty( $_post->activities['user_id'] ) ) {
				$this->ap_ids['user_ids'][] = $_post->activities['user_id'];
			}
		}
		// Unique ids only.
		foreach ( (array) $this->ap_ids as $k => $ids ) {
			$this->ap_ids[ $k ] = array_unique( $ids );
		}
	}