Adding multiple values inside while loop

Question

As an example I have four input text boxes in a form. I am trying to calculate the cost of each item type (quantity * cost) and the compute a total of all items. I have placed the formula inside a while loop to calculate cost of all the possible items found in the form. I am not receiving any result in return for the total cost? Demo

php

if ($_SERVER['REQUEST_METHOD'] == 'POST'){
      $discount = $_POST['discount'];
      $i = 1;
      while(isset($_POST['quantity'.$i])){
          $quantity = $_POST['quantity'.$i];
          $cost = $_POST['cost'.$i];
          $total = $quantity * $cost;
          $i++;
      }

}

html

<div id="contact-area">
  <form action="" method="post">
    <label>Quantity:</label> <input type="text" name="quantity1" id="quantity1"> <label>Cost:</label><input type="text" name="cost1" id="cost1"><br /><br />
    <label>Quantity:</label> <input type="text" name="quantity2" id="quantity2"> <label>Cost:</label><input type="text" name="cost2" id="cost2"><br /><br />
  <br /><br />
  <input type="submit" value="Submit" >
  </form>

<?php
if ($_SERVER['REQUEST_METHOD'] == 'POST'){
  echo"<p>Amount Due: $". $total ."</p>";
}
?>
</div>

Barmar · Accepted Answer · 2014-06-11 14:59:47Z

3

You're re-assigning $total instead of adding to it, so the final total will just be from the last item. It should be:

$total += $quantity * $cost;
       ^

answered Jun 11, 2014 at 14:59

Barmar

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Comments

Richard Parnaby-King · Accepted Answer · 2014-06-11 15:00:24Z

1

Your $total variable is being over-written every loop.

It should be:

$total += ($quantity * $cost);

answered Jun 11, 2014 at 15:00

Richard Parnaby-King

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Comments

Marcin Nabiałek · Accepted Answer · 2014-06-11 15:00:53Z

1

You need to add

$total = 0;

before while loop and in loop change

$total = $quantity * $cost;

to

$total += $quantity * $cost;

answered Jun 11, 2014 at 15:00

Marcin Nabiałek

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Comments

RibeiroSt · Accepted Answer · 2014-06-11 15:03:36Z

1

Try this:

if ($_SERVER['REQUEST_METHOD'] == 'POST'){
  $discount = $_POST['discount'];
  $i = 1;
  $total = 0;
  while(isset($_POST['quantity'.$i])){
      $quantity = $_POST['quantity'.$i];
      $cost = $_POST['cost'.$i];
      $total += $quantity * $cost;
      $i++;
  }

}

answered Jun 11, 2014 at 15:03

RibeiroSt

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Comments

Giacomo1968 · Accepted Answer · 2014-06-11 15:03:29Z

0

Rewriting your code like this will resolve the issue:

if ($_SERVER['REQUEST_METHOD'] == 'POST'){
      $discount = $_POST['discount'];
      $i = 1;
      $total = 0;
      while(isset($_POST['quantity'.$i])){
          $total += $_POST['quantity'.$i] * $_POST['cost'.$i];
          $i++;
      }

}

This is what was changed:

Adding a $total = 0; before the while loop to ensure that variable is assigned no matter what.
Removing the $quantity = $_POST['quantity'.$i]; & $cost = $_POST['cost'.$i]; since those are superfluous duplications of values that can be accessed directly.
Changing $total = to $total += so the $total is actually accumulated in the variable.

answered Jun 11, 2014 at 15:03

Giacomo1968

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