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<?php $in = array(); for($i = 1; $i <=5; $i++) { $in[] = 'category_id'; } $res = array();// Array where we will write result $t = &$res; // Link to first level foreach ($in as $key =>$k) { // Walk through source array if (empty($t[$k])) { // Check if current level has required key $t[$k] = []; // If does not, create empty array there $t = &$t[$k]; // And link to it now. So each time it is link to deepest level. } } unset($t); // Drop link to last (most deep) level var_dump($res);
Output for 7.3.0 - 7.3.28, 7.4.0 - 7.4.16, 8.0.0 - 8.0.3
array(1) { ["category_id"]=> array(1) { ["category_id"]=> array(1) { ["category_id"]=> array(1) { ["category_id"]=> array(1) { ["category_id"]=> array(0) { } } } } } }