PHP, SNMP, and Macs

I'm posting this question here, but if someone knows a better place to post this, please let me know. I've got everything running with SNMP, thanks for everyone's help, but I have a question about the limitations of PHP's SNMP. I was wanting to use this to be able to dynamically gather information about the computers we have. The majority of computers are Macintosh, and I have them set up with MacSNMP. MacSNMP has 3 MIB files, MIB_II, Mac_OS_MIB, and AppleTalk_MIB_II. When I do snmpwalk() I get back the information from the MIB_II, but not from the others. So then I tried to call upon a specific Object ID by it's number, that is located within the MAC_OS_MIB, I get an error. Warning: This name does not exist: system.sysUpTime.6.1.4.1.63.1.1.11 in /home/httpd/html/snmpget.php on line 11 snmpget failed! The question I have is if I give it the Object ID number, shouldn't it find it? Is PHP set to only grab certain Object ID's, and this ID has not been implemented into the PHP code? If that is the case, then how do I go about adding it? I wouldn't think that Apple would spend the time creating the SNMP software and make it so that most of the information can't be accessed via SNMP, but with Apple you never know. Thanks, Mike