<?php
ob_start();
  function GetRandStr($length){
  $str='abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
  $len=strlen($str)-1;
  $randstr='';
  for($i=0;$i<$length;$i++){
  $num=mt_rand(0,$len);
  $randstr .= $str[$num];
  }
  return $randstr;
  }

     $url = 'https://test-openapi-hk.qfapi.com';
     $api_type = '/trade/v1/payment';
     $pay_type = '805812';
     //$mchid = "MNxMp11FV35qQN"; //Only agents must provide this parameter
     $app_code = 'FB39698329554171A179031DCAE6EEE7'; //API credentials are provided by QFPay
     $app_key = 'C5856334C6624CEBB1A5C7307718E93D'; //API credentials are provided by QFPay
     $now_time = date("Y-m-d H:i:s"); //Get current date-time

     $fields_string = '';
     $fields = array(
        //'mchid' => urlencode($mchid),
      'pay_type' => urlencode($pay_type),
        'out_trade_no' => urlencode(GetRandStr(20)),
      'txcurrcd' => urlencode('HKD'),
        'txamt' => urlencode(2200),
        'txdtm' => $now_time
    );
    ksort($fields); //Ascending dictionary sorting A-Z
    print_r($fields);

    foreach($fields as $key=>$value) { 
    $fields_string .= $key.'='.$value.'&' ;
  }
  $fields_string = substr($fields_string , 0 , strlen($fields_string) - 1);

  $sign = strtoupper(md5($fields_string . $app_key));

  //// Header ////
  $header = array();
  $header[] = 'X-QF-APPCODE: ' . $app_code;
  $header[] = 'X-QF-SIGN: ' . $sign;

  //Post Data
  $ch = curl_init();
  curl_setopt($ch, CURLOPT_URL, $url . $api_type);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
  curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $fields_string);
  $output = curl_exec($ch);
  curl_close($ch);    

  $final_data = json_decode($output, true);
  echo "<pre>";
  print_r($final_data);
  echo "<pre>";
ob_end_flush();
?>