Online PHP editor | refs for gMIIU

<?php $arr =[ "id" => "integer:>0", "interval_id" => "string:!empty", "miles" => "integer:optional", "kms" => "integer:optional", "created_by" => "string:!empty|null", "created_at" => "integer:>0|null", "updated_by" => "string:!empty|null", "updated_at" => "integer:>0|null" ]; foreach ($arr as $key => $value) { // echo $key, "==>", $value, "\n"; if ( substr_count($value, 'optional')){ echo $key, "\n"; } }