struggling to break apart array for math

[turpentyne]

I have to take over somebody else's project. So I have the combination of being a beginner, not understanding their code well, and not experienced with arrays. I'm in over my head.

 

I have an array passed to the page, that would be something like this:

 

Array ( [215] => [213] => 1 [212] => 2 [214] => )

the user chose 1 person in 213, and 2 people in 212

 

and I basically need to break it apart to do math like this:

 

(#people x cost of 213 = totalcostA )  +  (# people x cost of 212 = totalcostB)  =  total

 

The broken down data goes into the database, and the total is used for the cart.

 

I've taken suggestions and gotten to this jumbled mess:

$ids = $_POST['workshop_id'];
print_r($_POST['participantqty']);
// the above shows the arrays  are sending to this page and printing correctly: Array ( [215] => [213] => 1 [212] => 2 [214] => ) 
foreach ($_POST['workshop_id'] as $id){
   $qty = $_POST['participatqty'][$id];
}

if(sizeof($_POST['workshop_id'])) {
// loop through array 
$number = count($ids); 
for ($i=0; $i<=$number; $i++) 
{ 
    // store a single item number and description in local variables 
    $itno = $ids[$i];
    $qty_insert = $qty[$i];

   

		$query_insertItemWorkshop = "INSERT INTO tbl_registration_workshop (registration_id, workshop_id, regworkshop_qty) VALUES ('$reg_id', '$itno', '$qty_insert')"; 
		$dberror = "";
		$ret = mysql_query($query_insertItemWorkshop);
	$query_selectAllItems_events = 'SELECT * FROM tbl_workshops where workshop_id = '.$itno;
@$result_all_events = mysql_query($query_selectAllItems_events);
@$numRows_all_events = mysql_num_rows($result_all_events);
@$num=mysql_num_rows($result_all_events); 
@$z_row = mysql_fetch_array($result_all_events);
// I want the below to work, but it won't until I can figure out how to break it all down.
$qty_total=$qty_insert*$z_row['workshop_price'];
$total = $total + $qty_total;

    
    if ($ids[$i] <> '') { 

// I want the info to also appear below, but  can't until I figure out how to break them down.

    echo $total_students;
echo "<tr><td valign=top><b>Description:</b> ". $z_row['workshop_title'] ."</td><td align='right' colspan='2' width=300 valign=top>" . $qty_insert . " at ". $z_row['workshop_price'] ." each:  </td><td valign=top> $". $qty_total ."</td></tr>";

 

[ignace]

Since there is too much code to figure out where you are actually multiplying/adding the totals, here's some example code:

 

echo calculate_total(array(215 => '', 213 => 1, 212 => 2, 214 => ''));

function calculate_total(array $array) {
  $total = 0;
  foreach (array_filter($array) as $key => $value) {
    $total += $key * $value;
  }
  return $total;
}

 

The function cleans the array of unwanted values (empty). Then for each of the remaining values it will multiply the key with it's value and add it to the total.