You forgot double quotes around OID passed to aboveZero function, so script ends up with syntax error. And you can shorten the script to just
function aboveZero will be called only if first condition is true, because NXSL uses short-circuit expression evaluation (http://en.wikipedia.org/wiki/Short-circuit_evaluation).
Best regards,
Victor
Code Select
return ($node->snmpOID == ".1.3.6.1.4.1.25506.1.1") && aboveZero(".1.3.6.1.4.1.25506.2.6.1.1.1.1.6.47");
function aboveZero will be called only if first condition is true, because NXSL uses short-circuit expression evaluation (http://en.wikipedia.org/wiki/Short-circuit_evaluation).
Best regards,
Victor