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Convert a DB result of parent/child items into a hierarchical array
<?php
// -- Only one caveat : The results must be ordered so that an item's parent will be processed first.
// -- Simulate a DB result
$results = array();
$results[] = array('id' => 'a', 'parent' => '', 'name' => 'Johnny');
$results[] = array('id' => 'b', 'parent' => 'a', 'name' => 'Bobby');
$results[] = array('id' => 'c', 'parent' => 'b', 'name' => 'Marky');
$results[] = array('id' => 'd', 'parent' => 'a', 'name' => 'Ricky');
$results[] = array('id' => 'e', 'parent' => '', 'name' => 'Timmy');
$results[] = array('id' => 'g', 'parent' => 'f', 'name' => 'Mary'); // -- Child is here before parent to demonstrate the second pass working
$results[] = array('id' => 'f', 'parent' => 'e', 'name' => 'Tommy');
$results[] = array('id' => 'h', 'parent' => 'b', 'name' => 'Donny');
function convertToHierarchy($results, $idField='id', $parentIdField='parent', $childrenField='children') {
$hierarchy = array(); // -- Stores the final data
$itemReferences = array(); // -- temporary array, storing references to all items in a single-dimention
foreach ( $results as $item ) {
$id = $item[$idField];
$parentId = $item[$parentIdField];
if (isset($itemReferences[$parentId])) { // parent exists
$itemReferences[$parentId][$childrenField][$id] = $item; // assign item to parent
$itemReferences[$id] =& $itemReferences[$parentId][$childrenField][$id]; // reference parent's item in single-dimentional array
} elseif (!$parentId || !isset($hierarchy[$parentId])) { // -- parent Id empty or does not exist. Add it to the root
$hierarchy[$id] = $item;
$itemReferences[$id] =& $hierarchy[$id];
}
}
unset($results, $item, $id, $parentId);
// -- Run through the root one more time. If any child got added before it's parent, fix it.
foreach ( $hierarchy as $id => &$item ) {
$parentId = $item[$parentIdField];
if ( isset($itemReferences[$parentId] ) ) { // -- parent DOES exist
$itemReferences[$parentId][$childrenField][$id] = $item; // -- assign it to the parent's list of children
unset($hierarchy[$id]); // -- remove it from the root of the hierarchy
}
}
unset($itemReferences, $id, $item, $parentId);
return $hierarchy;
}
print_r(convertToHierarchy($results));
?>
@manusiakemos

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commented May 9, 2019

thank's a lot

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