update total price based on selection mysql php

Hello I hope someone can help me. I need to know how to write a query which will allow me to add a value based on fuel quantity selection.

For example say user sel开发者_如何学JAVAects 100 litres then add £5 to total or if they select 500 litres then add £15 etc.

Here is the code i currently have for calculating price per litre.

// show price
        $fuelPriceQuery = sprintf("SELECT `Price` FROM fuel_price WHERE FuelType = '%s' LIMIT 1",
                    mysql_real_escape_string($_POST['fueltype']));

        $fuelPriceResult = mysql_query($fuelPriceQuery);
        $price           = mysql_fetch_array($fuelPriceResult, MYSQLI_ASSOC);

        echo 'The Price Today is £'.($_POST['qtylitres'] * $price['Price']);
        echo "<br />";
        echo "For " . ($_POST['qtylitres']) . " Litres of " .($_POST['fueltype']);

echo "<br />" . "<br />";

if(mysql_num_rows(mysql_query("SELECT * FROM subscribe WHERE Email = '".mysql_real_escape_string($_POST['inputEmail'])."'")))
{
     echo "Thanks but we already have your email";
}   
else
{

---

Extend your Code by this snippet, if i understand you right it should do exactly what you wanted.

[...]
if($_POST['qtylitres'] >= 100)
  $fee = 5;
if($_POST['qtylitres'] >= 500)
  $fee = 15;

echo 'The Price Today is £'.(($_POST['qtylitres'] * $price['Price'])+$fee);
[...]