Returns a connection identifier on success, or
ifx_connect() establishes a connection to an
Informix server. All of the arguments are optional, and if
they're missing, defaults are taken from values supplied in configuration file
(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).
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().
$conn_id = ifx_connect ("mydb@ol_srv1", "imyself", "mypassword");