Open a persistent connection to an Ingres II database.
There are only 2 differences between this function and ingres_connect() : First, when connecting, the function will first try to find a (persistent) link that's already opened with the same parameters. If one is found, an identifier for it will be returned instead of opening a new connection. Second, the connection to the Ingres server will not be closed when the execution of the script ends. Instead, the link will remain open for future use (ingres_close() will not close links established by ingres_pconnect()). This type of link is therefore called 'persistent'.
The database name. Must follows the syntax
The Ingres user name.
The password associated with username.