I have this source array():
$source[]
[
["user_id": 1, "item_id": 991, "quantity": 100],
["user_id": 1, "item_id": 992, "quantity": 50],
["user_id": 1, "item_id": 993, "quantity": 300],
["user_id": 1, "item_id": 992, "quantity": 150],
["user_id": 2, "item_id": 991, "quantity": 75],
["user_id": 2, "item_id": 992, "quantity": 20],
["user_id": 3, "item_id": 991, "quantity": 200],
["user_id": 3, "item_id": 992, "quantity": 425],
["user_id": 3, "item_id": 991, "quantity": 100],
["user_id": 3, "item_id": 992, "quantity": 75]
]
My goal is to reduce it so that i get only 1 item where user_id & item_id are the same:
$result[]
[
["user_id": 1, "item_id": 991, "quantity": 100],
["user_id": 1, "item_id": 992, "quantity": 200],
["user_id": 1, "item_id": 993, "quantity": 300],
["user_id": 2, "item_id": 991, "quantity": 75],
["user_id": 2, "item_id": 992, "quantity": 20],
["user_id": 3, "item_id": 991, "quantity": 300],
["user_id": 3, "item_id": 992, "quantity": 500]
]
The ultimate way would be to use an array_reduce, but i’ll take a foreach loop.
I’ve tried this, but i get an empty array
$result = array_reduce($source, function($a, $b)
{
if (($a->user_id === $b->user_id) && ($a->item_id === $b->item_id))
{
$a->quantity += $b->quantity; return $a;
}
else
{
return $b;
}
}, []);
or this, but i get an array with user_id as index and quantity as value as a overall total, not seperate by item_id:
$result = array_reduce($source, function($a, $b)
{
(($a[$b["user_id"]] = $a[$b["user_id"]]) && ($a[$b["item_id"]] = $a[$b["item_id"]])) ?? 0;
$a[$b["user_id"]] += $b["quantity"];
return $a;
}, []);
I’m starting to try with a foreach loop with if (isset[...]) but i feel like it will return true whatever the index of the $result[] array.
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Answer
You can use array_reduce function in next way:
$res = array_reduce (
$source,
function($res, $el) {
if (isset($res[$el['user_id'].$el['item_id']])) {
// if user_id with item_id exist
// increase quantity by $el['quantity']
$res[$el['user_id'].$el['item_id']]['quantity'] += $el['quantity'];
} else {
// create record with unique key for each user_id & item_id
// using concatenation
$res[$el['user_id'].$el['item_id']] = $el;
}
return $res;
},
[] // initial result - empty array
);
// output result values without keys
print_r(array_values($res));