Price Calculator based on Quantity

Question

I am trying to create a simple script to add to my html website.

I need it to calculate the price based on the quantity the user inputs.

For example, a value of 1-1000 will be multiplied by 1.50 and displayed, 1001-5000 multiplied by 1.20 and displayed, 5001-10000 multiplied by 1 and displayed and any number above that would display an error message like "Must be below 10000".

I've been trying to do this in php with no success.

Answer 1

You can use if to to check the vault and diplay the calculated value:

if($input <= 1000)
{
  echo $input * 1.5;
}
elseif($input <= 5000)
{
  echo $input * 1.2;
}
elseif($input <= 10000)
{
  echo $input;
}
else
{
  echo "Must be below 10000";
}

Answer 2

You may find operator switch very useful (Switch in PHP). Something like this:

...
switch ($quantity) {
    case (($quantity >= 1) && ($quantity <= 1000)):
        $multiplicator = 1.5;
        echo $quantity * $multiplicator;
        break;
    case (($quantity >= 1001) && ($quantity <= 5000)):
        $multiplicator = 1.2;
        echo $quantity * $multiplicator;
        break;
    case (($quantity >= 5001) && ($quantity <= 10000)):
        $multiplicator = 1.2;
        echo $quantity * $multiplicator;
        break;
    case ($quantity > 10000):
        echo 'Quantity must be less then 10000!';
        break;
}
....

Edited: another option using loop:

...
$limits_array = array(
    0 => array(
        'min' => 1,
        'max' => 1000,
        'mul' => 1.5,
    ),
    1 => array(
        'min' => 1001,
        'max' => 5000,
        'mul' => 1.2,
    ),
    2 => array(
        'min' => 5001,
        'max' => 10000,
        'mul' => 1,
    ),
);
foreach ($limits_array as $limits)
    if (($quantity >= $limits['min']) && ($quantity <= $limits['max']) {
        echo $quantity * $limits['mul'];
        break;
    }
if ($quantity > $limits['max'])
    echo 'Quantity must be less then 10000!';
...

Please notice, that after foreach last value element ($value is a common name for it, there it is $limits) still stores the last item from array. Take a look at brackets.

Answer 3

Instead of defining every condition in an IF statement, I would suggest defining constants for every stage:

<form action="" method="post">
    <input type="text" name="qnt" />
    <input type="submit" />
</form>

<?php

define('MIN_STAGE', 1);
define('MAX_STAGE', 3);
define('STAGE_1_MIN', 0);
define('STAGE_1_MAX', 1000);
define('STAGE_1_MULTIPLIER', 1.50);
define('STAGE_2_MIN', STAGE_1_MAX);
define('STAGE_2_MAX', 5000);
define('STAGE_2_MULTIPLIER', 1.20);
define('STAGE_3_MIN', STAGE_2_MAX);
define('STAGE_3_MAX', 10000);
define('STAGE_3_MULTIPLIER', 1);

for($i = MIN_STAGE; $i <= MAX_STAGE; $i++) {
    if ($_POST['qnt'] > constant("STAGE_".$i."_MIN") && $_POST['qnt'] <= constant("STAGE_".$i."_MAX")) {
        echo $_POST['qnt'] * constant("STAGE_".$i."_MULTIPLIER");
    }
    elseif ($_POST['qnt'] < constant("STAGE_".MIN_STAGE."_MIN") || $_POST['qnt'] > constant("STAGE_".MAX_STAGE."_MAX")) {
        die ('Must be between ' . constant("STAGE_".MIN_STAGE."_MIN") . ' AND ' . constant("STAGE_".MAX_STAGE."_MAX"));
    }
}

Answer 4

If you want it in pure php - that is not so good. To many reloads, but here how it works(it's a bad code, for bad idea):

<?php
$price = 10;
if(isset($_REQUEST['count']){
    $count = (int)$count;
    if($count > 10000){
        echo 'Must be below 10000';
    }
    elseif($count >= 1 && $count <= 1000){
        $price *= 1.2;
    }
    //Etc...
    $total = $price * $count;
}

In my opinion, you should try achieve it with JS(or easier - with jQuery). First of all, create a form:

<input type="text" id="count" />
<input type="button" id="calculate" value="Calculate" />

Then do something like this:

$(function(){
    var price = 10;
    var multiplier = 1;
    $('#calculate').click(function(){
        var count = parseInt($('#count').val());
        if(count > 10000){
            alert('Must be below 10000');
            return;
        }
        else if(count >= 1 && count <= 1000){
            multiplier = 1.2;
        }
        alert('Current price is ' + price + ' * ' + multiplier + ' = ' + getActualPrice());
    });

    function getActualPrice(){
        return price * multiplier;
    }
});

Fiddle