Freeagent OAuth2.0 in PHP

hi all,

for freeagent api integration suggest to use
adoy/OAuth2.0 extension.
so I used the same extension for freeagent api.
but I am facing problem in creating new resource by using POST method.I am
not able to send POST method input values.
anybody please help me how to send request body using adoy/OAuth2.0 for php.

thanking you