Online PHP editor | output for l7fso

<?php $array = array( 55 => array( 'ident' => 'test 1', ), 77 => array( 'parent_id' => 55, 'ident' => 'test 2', ), 109 => array( 'parent_id' => 77, 'ident' => 'test 3', , ), 78 => array( 'parent_id' => 55, 'ident' => 'test 4', ), 25 => array( 'ident' => 'test 5', ) ); foreach ($array as $key => &$sub) { if (isset($sub['parent_id'])) { $array[$sub['parent_id']]['children'][$key] = &$sub; } } unset($sub); // unset the reference to make sure to not overwrite it later... // now remove the entries with parents foreach ($array as $key => $sub) { if (isset($sub['parent_id'])) unset($array[$key]); } var_dump($array);