SNMP core php extension Formula was removed
Last version was
php54-snmp requires the following formulae to be installed:
autoconf 2.69 Automatic configure script builder
net-snmp 5.7.3 Implements SNMP v1, v2c, and v3, using IPv4 and IPv6

Recent formula history

Mike McQuaid Deprecate tap.
ilovezfs php54-snmp: bottle revision to rebuild.
Andy Blyler Revert "php 5.5.34"
Andy Blyler php 5.5.34
Andy Blyler cleanup extension testing

Formula code at GitHub