ECHO_PAYMENT_ID — (partly documented)
Interchange 5.9.0:
Source: lib/Vend/Payment/ECHO.pm
Line 299 (context shows lines 289-303 in echo():274)
#::logDebug("echo called, args=" . ::uneval(\@_));
my (%actual) = map_actual();
my @errMsgs = ();
# Required for validation
if (! $user) {
$user = $opt->{id} ||
charge_param('id') ||
$::Variable->{ECHO_PAYMENT_ID} ||
$::Variable->{MV_PAYMENT_ID} ||
$::Variable->{CYBER_ID}
or push @errMsgs, "No payment ID found.";
}