PBX in DMZ

Hello everyone,
I would like to know, is it correct to put freePBX or hardware PBX to DMZ for security reason? What is the best practise? We have several local sip phones and sip phone app (like Zoiper or smth else) which will be connected to PBX. I considering to make port forwarding or put to DMZ.

Best practice for phone deployments is to create a separate VLAN for the phone system and phones and have those devices sit on that.