Returns the error text from the last MySQL function, or '' (the empty string) if no error occurred. If no link is explicitely passed to the function, the last successful open link will be used to retrieve the error message from the MySQL server.
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.
See also mysql_errno().