Nåt sånt här:
$result = mysql_query ( "SELECT COUNT(*) AS cntAntal FROM Medlemmar" );
$row = mysql_fetch_array ( $result );
echo "Antal medlemmar: " . $row[ 'cntAntal' ];
Eller:
$result = mysql_query ( "SELECT * FROM Medlemmar" );
echo "Antal medlemmar: " . mysql_num_rows ( $result );