Custom sorting array of arrays using two conditions - php

Question

I have the following array:
$arr = [
[
'user_id' => 1,
'product_id' => 1
],
[
'user_id' => 1,
'product_id' => 2
],
[
'user_id' => 1,
'product_id' => 3
],
[
'user_id' => 2,
'product_id' => 1
],
[
'user_id' => 2,
'product_id' => 2
],
[
'user_id' => 3,
'product_id' => 1
]
];
And I want to sort it so it looks like this:
$arr = [
[
'user_id' => 1,
'product_id' => 1
],
[
'user_id' => 2,
'product_id' => 1
],
[
'user_id' => 3,
'product_id' => 1
],
[
'user_id' => 1,
'product_id' => 2
],
[
'user_id' => 2,
'product_id' => 2
],
[
'user_id' => 1,
'product_id' => 3
]
];
So basically I need to order by product_id and user_id in such a way that it selects the lower number product_id from each user before proceeding to the next.
I tried to use usort but I couldn't get it to work.
usort($campaigns, function($a, $b){
if($a['product_id'] == $b['product_id']){
return 0;
}
if($a['product_id'] < $b['product_id']){
if($a['user_id'] == $b['user_id']){
return 1;
}
if($a['user_id'] < $a['user_id']){
return 0;
}
return -1;
}else{
if($a['user_id'] == $a['user_id']){
return -1;
}
if($a['user_id'] < $a['user_id']){
return 0;
}
return 1;
}
});
I also tried array_multisort but all I could get it to do is to order using the same order that I already retrieve from the database.

Answer 1

Assumption is your values is integers:
usort($campaigns, function($a, $b){
if($a['product_id'] == $b['product_id']){
return $a['user_id'] - $b['user_id'];
} else {
return $a['product_id'] - $b['product_id'];
}
});
Also you can use database ordering with ORDER BY product_id, user_id clause.

Answer 2

Solution using array_multisort function with "array of columns"(few sorting dimensions):
$userIds = $productIds = [];
foreach ($arr as $k => $v) {
$userIds[$k] = $v['user_id'];
$productIds[$k] = $v['product_id'];
}
array_multisort($productIds, SORT_ASC, $userIds, SORT_ASC, $arr);
print_r($arr);
The output:
Array
(
[0] => Array
(
[user_id] => 1
[product_id] => 1
)
[1] => Array
(
[user_id] => 2
[product_id] => 1
)
[2] => Array
(
[user_id] => 3
[product_id] => 1
)
[3] => Array
(
[user_id] => 1
[product_id] => 2
)
[4] => Array
(
[user_id] => 2
[product_id] => 2
)
[5] => Array
(
[user_id] => 1
[product_id] => 3
)
)

Answer 3

$arrTags = [
[
'user_id' => 1,
'product_id' => 1
],
[
'user_id' => 1,
'product_id' => 2
],
[
'user_id' => 1,
'product_id' => 3
],
[
'user_id' => 2,
'product_id' => 1
],
[
'user_id' => 2,
'product_id' => 2
],
[
'user_id' => 3,
'product_id' => 1
]
];
foreach($arrTags as $key => $row){
$userArray[$key] = $row['user_id'];
$productArray[$key] = $row['product_id'];
}
array_multisort($productArray, SORT_ASC, $userArray, SORT_ASC, $arrTags);
print_r($arrTags);
Output
Array
(
[0] => Array
(
[user_id] => 1
[product_id] => 1
)
[1] => Array
(
[user_id] => 2
[product_id] => 1
)
[2] => Array
(
[user_id] => 3
[product_id] => 1
)
[3] => Array
(
[user_id] => 1
[product_id] => 2
)
[4] => Array
(
[user_id] => 2
[product_id] => 2
)
[5] => Array
(
[user_id] => 1
[product_id] => 3
)
)
You can also check in online editor. Click Here