INSERT and UPDATE page examples?

I need to construct a set of admin pages for a website so internal users can
INSERT and UPDATE data for a group of related tables. I dont want to
re-invent the wheel on this and due to nested foreign key constraints, it's
not so straightforward.

Here's my example:

Project
---------
proj_id pkey
title varchar

Employees
-----------
empl_id pkey
dept_id fkey
name varchar

ProjEmployees (many employees on a project)
--------------
proj_id pkey/fkey
empl_id pkey/fkey

Department
-----------
dept_id pkey
name varchar

Creating a COMPLETE PROJECT involves populating all of these tables but
users dont think ahead and understand the dependencies. A person adding
Employees to a Project will have to search for that Employee and then add
them. Sometimes they will suddenly realize that they need to create (insert)
a new Employee before they can add them to a Project (add to ProjEmployees)
and maybe then have to create (insert) a new Department, and so on...

Are there some pre-existing examples for how to go about this in PHP/Psql?

Thanks,

-Aaron