Looking for advice/best practice on building objects from query results - php

Question

Im going to try my best to explain myself. Not 100% sure how to word this. I have data in multiple tables something like
tbl_rooms
tbl_tables
tbl_people_sitting_at_table
All these tables have there linking id's and what I want to do is build a "room" object and not query the db in the loops. Right now what i have is something like this
Pseudocode
foreach ($rooms as $room) {
$room->tables = get_all_the_table_by_room_id($room->room_id);
.....
foreach ($room->tables as $table) {
$table->people_sitting_at_table = get_all_the_people_by_table_id($table->table_id);
What I have work but I don't like the amount of queries required to build the object. Heres is an example what I am looking to send back
stdClass Object
(
[id] => 15
[room_name] => room_name
[tables] => Array
(
[0] => stdClass Object
(
[id] => 34
[table_name] => table_name
[people_sitting_at_table] => Array
(
[0] => stdClass Object
(
[id] => 45
[name] => name
What im having a hard time with is knowing how to organize all that if i was to get all the data up front.. If I get all the tables in the room and then all the people at all the tables how do i get the people nested under the right table efficiently
Not sure if this enough info to get my point across, if not let me know
Here is some SQL for the exaple
SET SQL_MODE="NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";
CREATE TABLE `tbl_people_sitting_at_table` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(100) NOT NULL,
`table_id` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;
INSERT INTO `tbl_people_sitting_at_table` (`id`, `name`, `table_id`) VALUES
(1, 'jim', 1),
(2, 'bob', 1);
CREATE TABLE `tbl_rooms` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(100) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;
INSERT INTO `tbl_rooms` (`id`, `name`) VALUES
(1, 'room one'),
(2, 'room two');
CREATE TABLE `tbl_tables` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(100) NOT NULL,
`room_id` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;
INSERT INTO `tbl_tables` (`id`, `name`, `room_id`) VALUES
(1, 'table one', 1),
(2, 'table two', 1);

Answer 1

I think you are looking for something called the model-mapper design pattern.
Your model is a simple class that stores the columns in the database. You create one model instance per row. The mapper does your actual sql queries, then loads each row into a new model instance. So for instance, you would have a Room model and a Room Mapper. Then you have a PersonRoom model and a PersonRoom mapper. The PersonRoom mapper would let you select all PersonRooms that have a given room ID.
One thing you can look at that does this for you is Doctrine. Alternatively, you can just write it yourself. I wrote a code generator so that I can just point the code generator at the table and it will write the model/mapper code for me. I can then just use the models and mappers.