PHP/mySQL - how to fetch nested rows into multidimensinal array

Question

Coming from another question of mine where I learnt not to EVER use db queries within loops I consequently have to learn how to fetch all the data in a convenient way before

Answer 1

The query should look something like this:

SELECT * FROM scales
INNER JOIN items ON scales.id = items.scale_id

If you want to iterate through with nested loops, you'll need to pull this data into an array - hopefully you're not pulling back so much that it'll eat up too much memory.

$scales = array();

while ($row = mysql_fetch_assoc($data))
{
    if (!isset($scales[$row['scale_id']]))
    {
        $row['items'] = array();
        $scales[$row['scale_id']] = $row;
    }

    $scales[$row['scale_id']]['items'][] = $row;
}

Then you can loop through:

foreach ($scales as $scale)
{
    foreach ($scale['items'] as $item)
        ; //... do stuff
}

Note: this is somewhat naive in that $scale and $item will both contain fields from BOTH tables... if that's a problem then you need to change the assignments in the loop above to pull out only the fields you want.

Answer 2

It might be easier to first get all the scales, then all the items.

//first get scales
while ($row = fetchrowfunctionhere()) {
    $scale = $scales->createFromArray($row);
}

//then get items
$lastId = null;
while ($row = fetchrowfunctionhere()) {
    $scaleId = $row['scaleID'];
    if ($lastId != $scaleId) {
        $scale = $scales->getByScaleId($scaleId);
    }
    $item = $items->createFromArray($row);
    $scale->addItem($item);
    $lastId = $scaleId;
}

or everything in one sql

$lastId = null;
while ($row = fetchrowfunctionhere()) {
    $scaleData = array_slice($row, 0, 5, true);
    $itemData = array_slice($row, 5, 5, true);
    $scaleId = $scaleData['scaleID'];
    if ($lastId != $scaleId) {
        $scale = $scales->createFromArray($scaleData);
    }
    $item = $items->createFromArray($itemData);
    $scale->addItem($item);
    $lastId = $scaleId;
}

everything as one happy array

while ($row = fetchrowfunctionhere()) {
    $scaleData = array_slice($row, 0, 5, true);
    $itemData = array_slice($row, 5, 5, true);
    $scaleId = $scaleData['scaleID'];
    if (!isset($scales[$scaleId])) {
        $scales[$scaleId] = $scaleData;
    }
    $itemId = $itemData['itemID'];
    $scales[$scaleId]['items'][$itemId] = $itemData;
}