What is the best way to group a php array? - php

Question

For example, I have this array:
$bills = array(
array("bill_id"=>"1", "product_id"=>"1", "total"=>"10"),
array("bill_id"=>"2", "product_id"=>"2", "total"=>"20"),
array("bill_id"=>"3", "product_id"=>"1", "total"=>"30"),
array("bill_id"=>"4", "product_id"=>"1", "total"=>"40"),
array("bill_id"=>"5", "product_id"=>"2", "total"=>"50")
);
We need to add the totals of each produdct into a single array, i.e. What is the best clean fast way to generate the following array from the above one:
$products = array(
array("product_id"=>"1", "total"=>"80"),
array("product_id"=>"2", "total"=>"70")
);

Answer 1

the fastest way to sum this is index array, something like this
$products = array();
foreach ($bills as $bill) {
$key = $bill['product_id'];
if (isset($products[$key])) {
$products[$key]['total'] += $bill['total'];
} else {
$products[$key] = $bill;
}
}
var_dump($products);
output
array(2) {
[1]=>
array(3) {
["bill_id"]=>
string(1) "1"
["product_id"]=>
string(1) "1"
["total"]=>
int(80)
}
[2]=>
array(3) {
["bill_id"]=>
string(1) "2"
["product_id"]=>
string(1) "2"
["total"]=>
int(70)
}
}
to browse the invoice list
foreach($products as $key=>$bill) {
var_dump($bill);
}

Answer 2

Thie simplest approach is a single-pass loop.
$byProduct = [];
foreach($bills as $bill)
{
$key = $bill['product_id'];
if (!isset($byProduct[$key])) {
$byProduct[$key] = [
'product_id' => $key,
'total' => 0
];
}
$byProduct[$key]['total'] += $bill['total'];
}
Result of var_dump($byProduct):
array(2) {
[1] =>
array(2) {
'product_id' =>
string(1) "1"
'total' =>
int(80)
}
[2] =>
array(2) {
'product_id' =>
string(1) "2"
'total' =>
int(70)
}
}
Another approach is to use array_walk but it is pretty much the same in terms of complexity:
$byProduct = [];
array_walk($bills, function(&$bill) use (&$byProduct) {
$key = $bill['product_id'];
if (!isset($byProduct[$key])) {
$byProduct[$key] = [
'product_id' => $key,
'total' => 0
];
}
$byProduct[$key]['total'] += $bill['total'];
});