int mysql_pconnect ([string hostname [:port] [:/path/to/socket] [, string username [, string password]]])
Returns: A positive MySQL persistent link identifier on success, or false on error.
mysql_pconnect() establishes a connection to a MySQL server. The following defaults are assumed for missing optional parameters: host:port = 'localhost:3306', username = name of the user that owns the server process and password = empty password.
The hostname string can also include a port number. eg. "hostname:port" or a path to a socket eg. ":/path/to/socket" for the localhost.
Note: Support for ":port" wass added in 3.0B4.
Support for the ":/path/to/socket" was added in 3.0.10.
mysql_pconnect() acts very much like mysql_connect() with two major differences.
First, when connecting, the function would first try to find a (persistent) link that's already open with the same host, username and password. If one is found, an identifier for it will be returned instead of opening a new connection.
Second, the connection to the SQL server will not be closed when the execution of the script ends. Instead, the link will remain open for future use (mysql_close() will not close links established by mysql_pconnect()).
This type of links is therefore called 'persistent'.