- base64_decode: documentation ( source)
<?php
$key = <<<SOMEDATA777
-----BEGIN RSA PRIVATE KEY-----
MIIBPQIBAAJBALqbHeRLCyOdykC5SDLqI49ArYGYG1mqaH9/GnWjGavZM02fos4l
c2w6tCchcUBNtJvGqKwhC5JEnx3RYoSX2ucCAwEAAQJBAKn6O+tFFDt4MtBsNcDz
GDsYDjQbCubNW+yvKbn4PJ0UZoEebwmvH1ouKaUuacJcsiQkKzTHleu4krYGUGO1
mEECIQD0dUhj71vb1rN1pmTOhQOGB9GN1mygcxaIFOWW8znLRwIhAMNqlfLijUs6
rY+h1pJa/3Fh1HTSOCCCCWA0NRFnMANhAiEAwddKGqxPO6goz26s2rHQlHQYr47K
vgPkZu2jDCo7trsCIQC/PSfRsnSkEqCX18GtKPCjfSH10WSsK5YRWAY3KcyLAQIh
AL70wdUu5jMm2ex5cZGkZLRB50yE6rBiHCd5W1WdTFoe
-----END RSA PRIVATE KEY-----
SOMEDATA777;
$msg = "<ObtainTicketResponse><message></message><prolongationPeriod>999999999</prolongationPeriod><responseCode>OK</responseCode><salt>1499261850167</salt><ticketId>1</ticketId><ticketProperties>licensee=ivikhnyc licenseType=0 </ticketProperties></ObtainTicketResponse>";
$pk = openssl_get_privatekey($key);
openssl_private_decrypt(base64_decode($data), $out, $pk);
echo $out;