how to retrieve value of a json check box using php
I have a json form field which has a check box as coded : 

    {"name":"Act","description":"Checkthis","type":"checkbox"}

can anyone tell me how to get this value of this check box  **IF it is checked** using php

here is the form:

    <iframe src='http://www.facebook.com/plugins/registration.php?
                        client_id=325340244194060&
                        redirect_uri=http://www.pingcampus.com/facebook_registration_plugin/store_user_data.php&
                        fields=[
                        {"name":"name"},
                        {"name":"email"},
                        {"name":"gender"},
                        {"name":"birthday"},
                        {"name":"captcha"},
                        {"name":"Act","description":"Checkthis","type":"checkbox"}
                        ]'
                        scrolling="auto"
                        frameborder="no"
                        style="border:none"
                        allowTransparency="true"
                        width="500"
                        height="600">
                </iframe>
how to retrieve value of a json check box using php
===

I have a json form field which has a check box as coded : 

    {"name":"Act","description":"Checkthis","type":"checkbox"}

can anyone tell me how to get this value of this check box  **IF it is checked** using php

here is the form:

    <iframe src='http://www.facebook.com/plugins/registration.php?
                        client_id=325340244194060&
                        redirect_uri=http://www.pingcampus.com/facebook_registration_plugin/store_user_data.php&
                        fields=[
                        {"name":"name"},
                        {"name":"email"},
                        {"name":"gender"},
                        {"name":"birthday"},
                        {"name":"captcha"},
                        {"name":"Act","description":"Checkthis","type":"checkbox"}
                        ]'
                        scrolling="auto"
                        frameborder="no"
                        style="border:none"
                        allowTransparency="true"
                        width="500"
                        height="600">
                </iframe>