ifx_close() closes the link to an Informix database that's associated with the specified link identifier. If the link identifier isn't specified, the last opened link is assumed.
Note that this isn't usually necessary, as non-persistent open links are automatically closed at the end of the script's execution.
ifx_close() will not close persistent links generated by ifx_pconnect().
$conn_id = ifx_connect ("mydb@ol_srv", "itsme", "mypassword");
/* ... some queries and stuff ... */