Online PHP editor | refs for IANDm

<?php $arr = array( array( 'id' => 1, 'parent_id' => 0, 'title' => 'Parent Page', 'children' => array( array( 'id' => 2, 'parent_id' => 1, 'title' => 'Sub Page', ), array( 'id' => 5, 'parent_id' => 1, 'title' => 'Sub Page 2', 'children' => array( array( 'id' => 7, 'parent_id' => 5, 'title' => 'Sub Page', ), array( 'id' => 8, 'parent_id' => 5, 'title' => 'Sub Page 2', ) ) ) ) ), array( 'id' => 4, 'parent_id' => 0, 'title' => 'Another Parent Page', ) ); function printAll($arr, $parent = []) { if (is_array($arr)) { foreach ($arr as $k => $v) { if (isset($v['id'])) { $parent[] = $v['id']; echo implode('.', $parent) . PHP_EOL; } if (isset($v['children'])) { printAll($v['children'], $parent); } array_pop($parent); } } } printAll($arr);