How can I be able to start a call between two extension by click of a button

Asterisk Asterisk APIs
1

I have a PHP project and I have a SIP physical handset e.g 100200 and an outbound phone e.g 2567…

Is it possible to initiate a call from the sip extension to the outbound phone with a click of a button?

2

Google “asterisk click to call” for how to initiate a call between two outbound destinations on Asterisk from an external application (typially a web server). Note that Asterisk does not use the term extension in they way you have used it.