PHP: How to create a jagged array structure to represent grouped records from a database

Question

This seems like a simple challenge, but I'm struggling.

I want to retrieve records using a join query on two database tables and represent them as an array of arrays, whereby each of the elements in the root array is a parent record and each nested element represents a child record.

The SQL query is working fine, and it returns a set of rows in which the channel_key column is a grouping column.

Here's my attempt at populating the array structure from the rows:

$rows = $db->get_results($query);
$key = '';
$programmes = array();

foreach ($rows as $row) {
    $programme = array(
        'title' => $row->title,
        'start' => $row->start,
        'duration' => $row->duration
    );

    $programmes[] = $programme;

    if ($key != $row->channel_key) {
        $channels[] = array(
            'key' => $row->channel_key,
            'programme' => $programmes
        );

        $key = $row->channel_key;
        $programmes = array();
    }
}

Unfortunately this only populates the root level arrays (the ones that correspond to the parent records).

Any suggestions please?

Thanks, Tim

Answer 1

You only have one programme in the $programmes array when you assign it to the channel.

An alternative would be to build the channel array with the channel_key.

e.g.

<?php
$channels = array();
foreach($rows as $row) {
    // Create the channel node if it doesn't exist
    if (!isset($channels[$row->channel_key])) {
        $channels[$row->channel_key] = array(
            'key' => $row->channel_key,
            'programme' => array()
        );
    }

    $programme = array(
        'title' => $row->title,
        'start' => $row->start,
        'duration' => $row->duration
    );

    // Add to the existing channel node.
    $channels[$row->channel_key]['programme'][] = $programme;
}

Answer 2

Simple solution can be.

$rows = $db->get_results($query);
$key = '';
$programmes = array();

foreach ($rows as $row) {
    $programme = array(
        'title' => $row->title,
        'start' => $row->start,
        'duration' => $row->duration
    );

$programmes[$row->channel_key][] = $programme;
}