PHP changes session ID on each request
===

This morning my local php starts behaving strangely: *the session ID changes on each request* (making sessions unusable).

The code:

    <?php
    session_start();

The same page is available through "localhost" and "test" which is a /etc/hosts entry for localhost.

Requesting this same file on "localhost": the PHPSESSID cookie stays the same; on "test" it changes on every request.

Absolutely **nothing** changed in my code (no BOM or buggy code) or in Apache's config. I may have updated PHP (5.4.4), but reverting to the previous version (5.4.1) showed the same behavior. The same code running on a remote server (php 5.3) has been running ok for ages.

It's probably a bug in PHP :( but before reporting, I want to be sure I didn't overlook anything.

Any idea?

TIA 

greg