PHP：基于国家/地区的内容插入和选择

I have been searching all over google, I found some good question here in stack overflow but they are not satisfying .

Let suppose a visitor is filling a form for selling something, I want to store his country name automatically by filtering their IP address in some kind of IP's array(correct me if i am wrong).

And when visitors land on website, I will filter their IP address in some kind of IP's array associated with country and assign their country name is a variable. Then where ever they go there will be like :

SELECT * FROM that WHERE country =  $country

I am showing my logic ! Is it possible ? If not what is the preferred way ?

Many Thanks

ip2nation

The above site gives us nice database, With high accuracy ! And the sample code will be like :

$sql = 'SELECT 
                c.country 
            FROM 
                ip2nationCountries c,
                ip2nation i 
            WHERE 
                i.ip < INET_ATON("'.$_SERVER['REMOTE_ADDR'].'") 
                AND 
                c.code = i.country 
            ORDER BY 
                i.ip DESC 
            LIMIT 0,1';

    list($countryName) = mysql_fetch_row(mysql_query($sql));

    // Output full country name
    echo $countryName;