## Tuesday, January 20, 2009

### 2 Line PHP Function To Convert CIDR Postfix to Netmask

This is a problem with lots of really ugly solutions. Here's one that works, producing the correct output when called as a parameter to long2ip:
function cidr2longnetmask($cidr) { if($cidr > 32 || $cidr < 0) { return false; }$netmask = pow(2,$cidr) - 1;$netmask = $netmask << (32 -$cidr);