PHP references in uasort function - php

Question

I have
$products = array(
"product1" => [
"a" => ["total" => 1],
"b" => ["total" => 3],
"c" => ["total" => 2],
],
"product2" => [
"d" => ["total" => 3],
"f" => ["total" => 2],
"e" => ["total" => 1],
],
"product3" => [
"g" => ["total" => 3]
],
);
theses are my products and my stocks for each warehouses (warehouse a has 1 item of product1...)
I want to sort each warehouse by stock for each products.
I've done that :
foreach ($products as &$stocks) {
uasort($stocks, function($elmt1, $elmt2) {
return $elmt2["total"] - $elmt1["total"];
});
}
where I print my new array :
array(3) {
["product1"]=>
array(3) {
["b"]=>
array(1) {
["total"]=>
int(3)
}
["c"]=>
array(1) {
["total"]=>
int(2)
}
["a"]=>
array(1) {
["total"]=>
int(1)
}
}
["product2"]=>
array(3) {
["d"]=>
array(1) {
["total"]=>
int(3)
}
["f"]=>
array(1) {
["total"]=>
int(2)
}
["e"]=>
array(1) {
["total"]=>
int(1)
}
}
["product3"]=>
&array(1) {
["g"]=>
array(1) {
["total"]=>
int(3)
}
}
}
It did my job but when I get a closer look I can see the "&" char in only one of the arrays.
Why ?

Answer 1

Due to the fact that $item - a reference to the last element of the array.
You can do this trick:
$array = ['a', 'b', 'c'];
foreach ($array as &$item) {
}
foreach ($array as $item) {
$item = 1;
}
var_dump($array);
Output:
array(3) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[2]=>
&int(1)
}
It's not terrible, as long as you do not start to use $item.
It is better to make a job with reference in different function
$array = ['a', 'b', 'c'];
$test = function () use (&$array) {
foreach ($array as &$item) {
}
};
$test();
var_dump($array);
Output:
array(3) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[2]=>
string(1) "c"
}
Or try this:
$products = array(
"product1" => [
"a" => ["total" => 1],
"b" => ["total" => 3],
"c" => ["total" => 2],
],
"product2" => [
"d" => ["total" => 3],
"f" => ["total" => 2],
"e" => ["total" => 1],
],
"product3" => [
"g" => ["total" => 3]
],
);
foreach ($products as $key=>$stocks) {
uasort($products[$key], function($elmt1, $elmt2) {
return $elmt2["total"] - $elmt1["total"];
});
}
var_dump($products);
Output:
array(3) {
["product1"]=>
array(3) {
["b"]=>
array(1) {
["total"]=>
int(3)
}
["c"]=>
array(1) {
["total"]=>
int(2)
}
["a"]=>
array(1) {
["total"]=>
int(1)
}
}
["product2"]=>
array(3) {
["d"]=>
array(1) {
["total"]=>
int(3)
}
["f"]=>
array(1) {
["total"]=>
int(2)
}
["e"]=>
array(1) {
["total"]=>
int(1)
}
}
["product3"]=>
array(1) {
["g"]=>
array(1) {
["total"]=>
int(3)
}
}
}