MySQL Function Reference contd..

string mysql_error ([ resource $link_identifier ] )
Returns the error text from the last MySQL function. Errors coming back from the MySQL database backend no longer issue warnings. Instead, use mysql_error() to retrieve the error text. Note that this function only returns the error text from the most recently executed MySQL function (not including mysql_error() and mysql_errno()), so if you want to use it, make sure you check the value before calling another MySQL function.
$link_identifier.
The MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect() is assumed. If no such link is found, it will try to create one as if mysql_connect() was called with no arguments. If by chance no connection is found or established, an E_WARNING level error is generated.
Return value.
Returns the error text from the last MySQL function, or '' (empty string) if no error occurred.

int mysql_errno ([ resource $link_identifier ] )
Returns the error number from the last MySQL function or 0 (zero) if no error occurred.
bool mysql_close ([ resource $link_identifier ] )
closes the non-persistent connection to the MySQL server that's associated with the specified link identifier. If link_identifier isn't specified, the last opened link is used.
Return value.
Returns TRUE on success or FALSE on failure.