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 warning is generated.
Returns a string with the status for uptime, threads, queries, open tables,
flush tables and queries per second. For a complete list of other status
variables, you have to use the SHOW STATUS SQL command.
If link_identifier is invalid, NULL is returned.