You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
Backtrace | Query

1. /home/zrsweb/zrsweb/public_html/system/mysql.php (line 127)
   execq(

   [
     "select id_visitor from visitors where `sid`="
   ]

   );
2. /home/zrsweb/zrsweb/public_html/download.php (line 12)
   __(

   [
     "select id_visitor from visitors where `sid`="
   ]

   );

select id_visitor from visitors where `sid`=