- sprintf: documentation ( source)
<?php
$partner['id_partner'] = 121;
$partner['id_partner_site'] = 432;
$partner['id_partner_banner'] = 32;
$code = 123;
$PID = sprintf('%d_%d_%d_%d', $partner['id_partner'], $partner['id_partner_site'], $partner['id_partner_banner'], $code);
echo $PID;