There seems to be more than SNMP_OID_OUTPUT_FULL and SNMP_OID_OUTPUT_NUMERIC.
For example, when I walk on BRIDGE-MIB::dot1dTpFdbPort without setting the output format and var_dump the result, I get output like:
["BRIDGE-MIB::dot1dTpFdbPort.'..F8.7'"]=>
string(2) "52"
When I set it to NUMERIC, I get what I expected:
[".1.3.6.1.2.1.17.4.3.1.2.244.206.70.56.24.55"]=>
string(2) "52"
When I set it to FULL, I get even more (line-wrapped manually):
[".iso.org.dod.internet.mgmt.mib-2 .dot1dBridge.dot1dTp .dot1dTpFdbTable .dot1dTpFdbEntry .dot1dTpFdbPort. '..F8.7'"]=>
string(2) "52"
