Thank you very much for the quick answer.
I have done it, but still have a problem.
Like you you check
checkphone.org/?TAC=0
returns right result, because TAC exists, but when I open page without any variables like this:
checkphone.org/
It returns error:
1064 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 ''%') LIMIT 0, 100' at line 1 SQL=select DISTINCT * from t8dsv_phones where TAC like CONCAT(,'%') LIMIT 0, 100
because there is no TAC variable and {$REQUEST:VAR_NAME} is empty.
this is an SQL request:
select DISTINCT * from t8dsv_phones where TAC like CONCAT({$REQUEST:TAC},'%') LIMIT 0, 100
Could you please advise.