On the ZetCode.com site there's a five part tutorial posted about getting your PHP application up and running on a PostgreSQL database (updated on the 4th).

This is a PHP tutorial for the PostgreSQL database. It covers the basics of PostgreSQL programming with PHP. The examples were created and tested on Linux. [...] PostgreSQL is a powerful, open source object-relational database system. It is a multi-user, multi-threaded database management system. It runs on multiple platforms including Linux, FreeBSD, Solaris, Microsoft Windows and Mac OS X. PostgreSQL is developed by the PostgreSQL Global Development Group.

The chapters guide you through every step you'll need:

• An introduction to PostgreSQL and getting it and PHP support installed (with the php5-pgsql package)
• Example code showing how to extract data from your tables
• Working with images and storing their data in a table
• Pulling out the metadata from the database, things like number of rows returned and table information
• Transactions and database-side processing