X-PH-, Plivo will send these SIP headers with the HTTP request.
Outbound calls
For outbound calls, you can set custom SIP headers while :- Making an outbound call
- Using the nested Number element of the Dial element
- Using the nested User element of the Dial element
Inbound calls
For inbound calls, you need a SIP phone that allows custom SIP headers. If you have one, SIP headers that start withX-PH- will sent as HTTP requests.