Mine

ob@ob-laptop-t43:~/src/webifpk$ grep -R -i 'nvram ' *|grep dhcp_enabled
etc/init.d/x50dnsmasq.webif:if [ -z $(nvram get lan_dhcp_enabled) ]; then
etc/init.d/x50dnsmasq.webif:    nvram set lan_dhcp_enabled=1
etc/init.d/x50dnsmasq.webif:    dhcp_enabled=$(nvram get ${ifname}_dhcp_enabled)
www/cgi-bin/webif/network-dhcpiface.sh:         FORM_dhcp_enabled=${FORM_dhcp_enabled:-$(nvram get ${FORM_iface}_dhcp_enabled)}