<?php
$resultsAsJson = '{
  "BillInquiryResult": {
    "ResponseCode": "0000",
    "HostDateTime": "2020-11-21T20:40:57+03:00",
    "Message_EN": "",
    "Message_TR": "",
    "CustomerName": "Y****K***",
    "BillList": [
      {
        "BillAmount": "30.1",
        "DueDate": "2020-11-16",
        "BillOrderNumber": "FD01050C7CC2AC",
        "BillInquiryId": "0"
      }
    ]
  }
}';
$results = json_decode($resultsAsJson, true);
for ($i = 0; $i < count($results["BillInquiryResult"]["BillList"]); $i++) {
    $res = $results["BillInquiryResult"]["BillList"][$i];
    echo $res["BillAmount"];
    echo "\\n";
    echo $res["BillOrderNumber"];
}
?>