- urldecode: documentation ( source)
<?php
echo urldecode('MerID=I0110DQX&OrderID=426&ResponseCode=3&ReasonCode=11&ReasonCodeDesc=Invalid+signature&PurchaseAmt=&PurchaseCurrency=&RRN=&AuthCode=&AmountRefunded=&AmountReversed=&ActualAmount=&AcqID=&Time=&IP=&Phone=&OrderDescription=&PaddedCardNo=&fee=&eci=&CountryBin=&CountryIP=&OnUs=&CountryPhone=&Signature=r4Ihr6%2Ffux5EPZ5ThFfUQMzZ%2F9A%3D');