How to multiply unknown number of php array values by each other?

Question

I have a database output loop.

I need to multiply values in $total, assign the result to another variable and output it. How should I do this?

$quantity comes from $_POST.

$items = implode(",",array_keys($_POST));

mysql_query('SET NAMES utf8');
$query = 'SELECT * FROM
    items
WHERE
    item_id IN (' . $items . ')';

$result = mysql_query($query, $db) or die (mysql_error($db));

echo ' 

<table id="items">
<tr class="head">
    <td>Name</td>
    <td>Cost</td>
    <td>Quantity</td>
    <td>Subtotal</td>
</tr>

';
$total = array ();  
while ($row = mysql_fetch_assoc($result)) {
echo '<tr class="targetfields">';
echo '<td>' . $row['item_name'] . '</td>

<td>' . $row['item_cost'];
//Getting item id
foreach ($_POST as $itemid=>$quantity)
{
//Displayin' quantity
if ($itemid == $row['item_id']){
    echo '</td><td><input name="' . $row['item_id'] . '" class="input-small" size="2" maxlength="2" type="text" value="';
    echo "{$quantity}";
    echo '" readonly></td>
    <td>'; $sum = ($row['item_cost'] * $quantity); echo $sum;
    echo '</td>';

    $total.= $sum;

}


}
        echo '</tr>';
}

?>  <tr>
<td class="sum" colspan="4">    Total: 
<?php 



?> </td>
</tr>
</table>

so you want multiplication of $row['item_cost'] * $quantity and store its calculation in array for each iteration? — Yogesh Suthar
– Yogesh Suthar, Commented Mar 25, 2013 at 7:48
@Yogesh Yes, exactly. I'm taking the array to store calculations of every iteration, then myltiplying every calculation by each other and output it. — Tony Montana
– Tony Montana, Commented Mar 25, 2013 at 7:56

Prasanth Bendra · Accepted Answer · 2013-03-25 07:23:17Z

2

$total .= $sum; this will not work change it to : $total[] = $sum;
To get the product all elements of array $total use : after while loop array_product

ie :

$items = implode(",",array_keys($_POST));

mysql_query('SET NAMES utf8');
$query = 'SELECT * FROM
    items
WHERE
    item_id IN (' . $items . ')';

$result = mysql_query($query, $db) or die (mysql_error($db));
$total = array ();  
while ($row = mysql_fetch_assoc($result)) {

$sum = ($row['item_cost'] * $quantity); echo $sum;      
$total[] = $sum;

}

echo array_product($total);

Ref: http://php.net/manual/en/function.array-product.php

answered Mar 25, 2013 at 7:23

Prasanth Bendra

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Comments

Yogesh Suthar · Accepted Answer · 2013-03-25 07:23:25Z

2

I think it should be

$sum = 1; 
while ($row = mysql_fetch_assoc($result)) {
    $sum = $row['item_cost'] * $sum; 
}
echo $sum;

answered Mar 25, 2013 at 7:23

Yogesh Suthar

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5 Comments

Prasanth Bendra Over a year ago

What about the $quantity ?

Yogesh Suthar Over a year ago

@PrasanthBendra there is no need for quantity.Because the multiplication will be of the rows selected from query. And main thing $quantity is never initialised here so it will create error here.

bestprogrammerintheworld Over a year ago

Wouldn't $sum be $row['item_cost'] * 1 at each row and echo $sum would only show the last calculation?

Yogesh Suthar Over a year ago

@bestprogrammerintheworld In each iteration it will assign the multiplication to $sum and in next iteration it will be used for multiplication.

bestprogrammerintheworld Over a year ago

Aha ok thanks! Sometimes the most basic things are not obvious enough :-)

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