I try to write a plugin and I need to add some fields under the write zone for each zone, in write or edit or save, or save as draft mode.
I have tried to imitate this wonderfull plugin :
because it can't help me but it put fields in the admin. I don't succeed.
Is there someone who know where there is a piece of code to include a php page already prepared in the admin panel (in a plugin context) ?
add_action ??? but how to write the arguments ?
Thanks in advance for any help