Problema attacco a script sql Injection

[robertes]

Ciao a tutti per prevenire eventuali attacchi SQL Injection potrebbe essere utile questo codice?

<?php 
// per ottenere l'url che ha generato l'errore
$where = "http://$HTTP_HOST$REQUEST_URI"; 
$ip= $_SERVER['REMOTE_ADDR'];
$query_string= $_SERVER['QUERY_STRING'];
$http_referrer= $_SERVER['HTTP_REFERER'];
echo "$where 
 $ip 
 $query_string 
 $http_referrer 
 $user_agent";

if (stristr($query_string,'+union+') OR stristr($query_string,'%20union%20') OR
stristr($query_string,'*/union/*') OR stristr($query_string,' union ') )
{
echo "Hai utilizzato il comando sql UNION";
exit();
}
if (stristr($query_string,'+select+') OR stristr($query_string,'%20select%20') OR
stristr($query_string,'*/select/*') OR stristr($query_string,' select ') )
{
echo "Hai utilizzato il comando sql SELECT";
exit();
}
if (stristr($query_string,'+delete+') OR stristr($query_string,'%20delete%20') OR
stristr($query_string,'*/delete/*') OR stristr($query_string,' delete ') )
{
echo "Hai utilizzato il comando sql DELETE";
exit();

}
if (stristr($query_string,'+drop+') OR stristr($query_string,'%20drop%20') OR
stristr($query_string,'*/drop/*') OR stristr($query_string,' drop ') )
{
echo "Hai utilizzato il comando sql DROP";
exit();

}
if (stristr($query_string,'+insert+') OR stristr($query_string,'%20insert%20') OR
stristr($query_string,'*/insert/*') OR stristr($query_string,' insert ') )
{
echo "Hai utilizzato il comando sql INSERT";
exit();

}
?>

grazie ciao