Checksum calculation algorithm for the Softbank payment service

softbank_checksum.php

<?php

/**
 * @file
 * Example checksum calculation for Softbank.
 */

// Example only. Real hash key value is provided by Softbank.
$hash_key = 'a2d8648d0246a924bed081433930f868c8100224';

// Build out the list of fields.
$post_fields = array(
  'pay_method' => 'credit',
  'merchant_id' => '99999',
  'service_id' => '001',
  'cust_code' => '9999999',
  'sps_cust_no' => '',
  'sps_payment_no' => '',
  'order_id' => '9999999999',
  'item_id' => '1',
  'pay_item_id' => '',
  'itemName' => '',
  'tax' => '',
  'amount' => '99999',
  'pay_type' => '0',
  'auto_charge_type' => '',
  'service_type' => '0',
  'div_settele' => '',
  'last_charge_month' => '',
  'camp_type' => '',
  'tracking_id' => '',
  'terminal_type' => '0',
  'successUrl' => 'https://example.com/payment/softbank/success',
  'cancelUrl' => 'https://example.com/payment/softbank/cancel',
  'errorUrl' => 'https://example.com/payment/softbank/fail',
  'pageconUrl' => 'https://example.com/payment/softbank/notify',
  'free_1' => '',
  'free_2' => '',
  'free_3' => '',
  'free_csv' => '',
  'request_date' => '20080505175959',
  'limit_second' => '',
);

// Concatenate the fields and convert encoding.
$post_fields_string = array_reduce($post_fields, function ($carry, $item) {
  return $carry . mb_convert_encoding($item, 'UTF-8', 'SJIS');
});

// Append the hashkey.
$post_fields_string = mb_convert_encoding($post_fields_string . $hash_key, 'UTF-8', 'SJIS');

// Calculate the hash.
$sps_hashcode = sha1($post_fields_string);