What is the difference between connect and pconnect in PHP?

mysql_connect opens up a database connection every time a page is loaded. mysql_pconnect opens up a connection, and keeps it open across multiple requests.

mysql_pconnect uses less resources, because it does not need to establish a database connection every time a page is loaded.

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()).

These type of links is therefore called 'persistent'.