Limiting IP access is a rather efficient way to restrict access to sensitive sites, such as for example phpmyadmin installations.There are multiple ways to archive this, one of the easyer ways is by setting the .htaccess file in the web directory for the specific site:
Deny from all
Allow from 127.0.0.1 # the local server
Allow from 10.25.8.0/22 # local subnet
Allow from 126.96.36.199/28 # internet subnet
Allow from 188.8.131.52 # single internet address
The above gives you a series of examples for a local subnet (local internal network), internet subnets or single address.