如何在PHP中提取非索引数组？

I have an array with this structure when I print_r() my json input with method post

 public function ajax_add($mode) {
    echo "<pre>";      
      print_r($this->input->post());
   echo "</pre>";
 }

this is my print_r result

    Array

(
    [{"thang":"2019","kd_kegiatan":"2409","kd_output":"014","kd_sub_output":"002","kd_komponen":"307","kd_sub_komponen":"B","nama_sub_komponen":"","kd_dept":"033","kd_unit":"04","kd_program":"08","id_paket":""}] => 
    [0] => 
)

I need to convert json data above to assosiative array for example

array(

   "thang"=>2019,
   "kd_kegiatan"=>2409
   "kd_output"=>014,
   "etc"=>"....."
)

but I don't know to doing that. because the first array have no index. how to fix that?