In order to use the SNMP functions requires installation of the » Net-SNMP package. SNMPv3 functions available only when » OpenSSL package is installed too.
On Windows SNMP functions are only available on NT and not on Win95/98.
Beginning with PHP 5.4.0 Net-SNMP version 5.3+ is required for Unix installations and Net-SNMP version 5.4+ for Windows.