$nsreverse
Get the domain name from the given IP address (Reverse DNS lookup)
Syntax:
$nsreverse( ipaddr )
Parameters:
ipaddr – IP address
Returns:
Domain name
Version Since:
3.8
Example:
$nsreverse( $addr ) = (.+)
Get the domian name of the remote IP address
$nsreverse( $addr ) = \.brekeke.com$
Check whether the remote host belongs to the specified domain.