The following descriptions discuss each of PHP's MySQL-related functions. Optional parameters are indicated by square brackets ().
Many functions take an optional link_id (link identifier) parameter that indicates a connection to a MySQL server. If the link identifier is missing from a function call, the most recently opened connection is used. Some functions will try to establish a connection if no connection is specified and there isn't one open.
A result_id parameter indicates a result set identifier, typically returned by mysql_db_query() or mysql_query().
Some functions produce an error message if an error occurs, in addition to returning a status value. In Web contexts, this message appears in the output sent to the client ...