As advised by thies@digicol.de here is my bug report.
(I was thinking of using php to create web application connecting to oracle in order to replace other tools .........)

1.
I am able to connect (as long as I use the env variable ORACLE_SID see 2.) and retreive data from oracle BUT the php.exe never ends even if I make a call to exit() in my php script.

I tried to locate where it hangs (don't know if it helps)
In oci8.c, a call to OCITransRollback (in _oci_conn_list_dtor) is never returning causing php.exe to hang for ever.

2.
I actually can not connect using alias in tnsnames.ora, I had to use the environment variable bound to my ORACLE_SID eg:

        // This Works OK:
        putenv("ORACLE_SID=db1"); // Local instance ID
        $conn = ocilogon("tigger","scott","");

        // This does *NOT* work:
        $conn = ocilogon("tigger","scott","dbalias"); // dbalias correctly configured and working with sqlplus.

Thanks.