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<?php $array = [ "category" => "Music", "items" => [ ["ID" => "1", "start_date" => "2018-11-20", "end_date" => "2018-11-28"], ["ID" => "2", "start_date" => "2018-11-22", "end_date" => "2018-11-28"], ["ID" => "3", "start_date" => "2018-11-26", "end_date" => "2018-11-30"], ["ID" => "4", "start_date" => "2018-11-27", "end_date" => "2018-11-31"], ["ID" => "4", "start_date" => "2018-11-29", "end_date" => "2018-11-31"] ] ]; $array["items"] = array_values( array_reduce( $array["items"], function ($carry, $row) { $carry[$row["end_date"]]["data"] = $row["end_date"]; $carry[$row["end_date"]][] = $row; return $carry; } ) ); var_export($array);