- array_map: documentation ( source)
- implode: documentation ( source)
- sprintf: documentation ( source)
- md5: documentation ( source)
<?php
$paramList = array();
$paramList['Shop_IDP'] = '1111111';
$paramList['Order_IDP'] = 125;
$paramList['Subtotal_P'] = sprintf('%.2f', (float)235.69);
$paramList['Parent_Order_IDP'] = 125;
$signaturePart = implode('&', array_map(function($param){return md5($param);}, $paramList));
echo $signaturePart;