function custom_mysql_query($sql)
{
    $GLOBAL['query_count'] ++;
    return mysql_query($sql);
}

mysql> SHOW STATUS LIKE 'Com_select';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Com_select    | 2     |
+---------------+-------+
1 row in set (0.00 sec)

SHOW STATUS LIKE 'Com_%';