@Lester
Good idea to compare your and my phpinfo().
Now I have found my mistake:
Every time I thought, the file php.ini in the
folder /php/ are used - but I'm wrong - the
"real" php.ini are located in the folder /apache/bin/
Mia culpa ;-)

@Milan
I have restarted my Apache many times ... ;-)

Yeah - now the FB is started. But my testscript
does not work. It appears the message:

Warning: ibase_connect() [function.ibase-connect]:
Unable to complete network request to host "localhost".
Failed to locate host machine. Undefined service
gds_db/tcp. in X:\htdocs\test.php on line 5
error in db connect

My testscript test.php is:
<?php
$host =
'localhost:C:/Programme/Firebird/Firebird_1_5/examples/EMPLOYEE.FDB';
$username = 'SYSDBA';
$password = 'masterkey';
$dbh = ibase_connect ( $host, $username, $password ) or die ("error
in db connect");
?>

Any idea?
Ublix