Well the sysntax is
int ibase_connect (string database [, string username [, string password [, string charset [, int buffers [, int dialect [, string role]]]]]])
Establishes a connection to an InterBase server. The database argument has to be a valid path to database file on the server it resides on. If the server is not local, it must be prefixed with either 'hostname:' (TCP/IP), '//hostname/' (NetBEUI) or 'hostname@' (IPX/SPX), depending on the connection protocol used. username and password can also be specified with PHP configuration directives ibase.default_user and ibase.default_password. charset is the default character set for a database. buffers is the number of database buffers to allocate for the server-side cache. If 0 or omitted, server chooses its own default. dialect selects the default SQL dialect for any statement executed within a connection, and it defaults to the highest one supported by client libraries.
Try with this :
ibase_connect('c:/interbase/bin/phptest.gdb','sysdba','masterkey','ISO8859_1',0,1);
I think the first parameter should be the file name of database(we've to pass the url)..
--Shastry