<p>I've been using PHP &amp; MySQL for ages and am about to start using PostgreSQL instead.</p>

<p>What's the preferred method?  </p>

<p>Is it via the PDO objects or is there something better?</p>

PDO objects are the new hotness.  I'd recommend that as long as you can ensure that your target platform will always be running PHP 5.2+.
There are many other database abstraction layers that support PostgreSQL that are compatible with older versions of PHP; I'd recommend
ADODB
.
You should really be using PDO or a different abstraction layer even for your MySQL work; that way you won't have this problem again!