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. All of the arguments are optional, and if they're missing, defaults are assumed ('localhost', user name of the user that owns the server process, 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'.