datadistrict.php

<?php 
$id_provinsi_terpilih=$_POST["id_provinsi"]; 
$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => "https://api.rajaongkir.com/starter/city?province=".$id_provinsi_terpilih,
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_HTTPHEADER => array(
    "key: dd5ac3282e0db821c498952f535539e1"
  ),
));

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  $array_response = json_decode($response, TRUE);
  $data_distrik=$array_response["rajaongkir"]["results"];

  echo "<option value=''>--Pilih Distrik--</option>";

  foreach ($data_distrik as $key => $tiap_distrik) 
  {
    echo "<option value='' 
    id_distrik='".$tiap_distrik["city_id"]."'
    nama_provinsi='".$tiap_distrik["province"]."' 
    nama_distrik='".$tiap_distrik["city_name"]."' 
    tipe_distrik='".$tiap_distrik["type"]."' 
    kodepos='".$tiap_distrik["postal_code"]."'>";
    echo $tiap_distrik["type"]. " ";
    echo $tiap_distrik["city_name"];
    echo "</option>";
  }
}

?>