Adding Across Arrays - php

Question

I structured the item information in an unorthodox way, it is stored in three different arrays and are related by the key. I am looking to Sum the Quantities by ItemID.
1. Array #1 ItemID
$_SESSION["item_id"][]
1 => 1, 2 => 1, 3 =>2
2. Array #2 Size
$_SESSION["size"][]
1 => S, 2 => L, 3 =>S
3. Array #3 Quantity
$_SESSION["count"][]
1 => 250, 2 =>750, 3=>250
The result should be as follows:
ItemID # 1 --> Quantity 1000
ItemID # 2 --> Quantity 250
Could someone could help me with a function ?

Answer 1

Let's say, you have the following array in $_SESSION:
$_SESSION['item_id'] = array(1, 1, 2);
$_SESSION['size'] = array('S', 'L', 'S');
$_SESSION['count'] = array(250, 750, 250);
NOTE: the following answer take assumption that array length in those 3 SESSION value are equal.
You will need to create new array to store the result:
$newArrayResult = array();
After that, you will need to do for...each loop to extract currently accessed key:
foreach($_SESSION['item_id'] as $key => $value){
//the logic goes here
}
Next, we will use item_id as our array key in $newArrayResult. To do that, we will need to check first, if it is already defined. If not, create the key with default value 0. We do the checking by using built in function called array_key_exists. This way, we will avoid running into undefined key index error.
if(!array_key_exists($value, $newArrayResult)){
$newArrayResult[$value] = 0;
}
After we have the key for $newArrayResult, next step would be to simply store count value into it:
$newArrayResult[$value] += $_SESSION['count'][$key];
Done. Print the result to test:
print_r($newArrayResult);
Here is the whole code again, for you to copy-paste. Don't forget to read and understand the above flow first:
$_SESSION['item_id'] = array(1, 1, 2);
$_SESSION['size'] = array('S', 'L', 'S');
$_SESSION['count'] = array(250, 750, 250);
$newArrayResult = array();
foreach($_SESSION['item_id'] as $key => $value){
if(!array_key_exists($value, $newArrayResult)){
$newArrayResult[$value] = 0;
}
$newArrayResult[$value] += $_SESSION['count'][$key];
}
print_r($newArrayResult);