Regex help needed

[aXeR]

Hi Guys,

 

We currently enforce some validation on our install for when a client sends an rDNS request into our system which is as follows:

 

$validate = "/^([a-zA-Z0-9_-])+(\.[a-zA-Z0-9_-]+)([a-zA-Z0-9_-])+(\.[a-zA-Z0-9_-]+)*\.([a-zA-Z]{2,6})$/";

 

I believe this forces something1.something2.something3

 

something1/2 can be anything where as something3 is limited to text and dots only (for the TLD) if I recall correctly.

 

The issue is, despite not being proper formatting, people often want to submit something.tld which our system currently blocks.

 

Can anyone suggest a correct syntex that will allow for:

 

something.tld

something.something.tld

something.something.something.tld

 

ETC?

 

Thanks!