ifx_connect() establishes a connection to an Informix server.
In case a second call is made to ifx_connect() with the same arguments, no new link will be established, but instead, the link identifier of the already opened link will be returned.
The link to the server will be closed as soon as the execution of the script ends, unless it's closed earlier by explicitly calling ifx_close().
All of the arguments are optional, and if they're missing, defaults are
taken from values supplied in php.ini (ifx.default_host for the host
(Informix libraries will use INFORMIXSERVER environment
value if not defined), ifx.default_user for user, ifx.default_password for
the password (none if not defined).
databaseThe database name, as a string.
useridThe username, as a string.
passwordThe password, as a string.