mysql_close() closes the non-persistent connection to
the MySQL server that's associated with the specified link identifier. If
isn't specified, the last opened
link is used.
Using mysql_close() isn't usually necessary,
as non-persistent open links are automatically closed at the end
of the script's execution. See also
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.