PHPでインデックスを使って配列を組み立てた際の動作

$list = [];
$list[2] = 'c';
$list[0] = 'a';
$list[1] = 'b';

foreach ($list as $index => $element)
{
    var_dump($index, $element);
}

int(2)
string(1) "c"
int(0)
string(1) "a"
int(1)
string(1) "b"

var list = [];
list[2] = "c";
list[0] = "a";
list[1] = "b";

list.forEach(function(element, index) {
  console.log(index, element);
});

0 "a"
1 "b"
2 "c"

$list = [];
$list[2] = 'c';
$list[0] = 'a';
$list[1] = 'b';
ksort($list);

foreach ($list as $index => $element)
{
    var_dump($index, $element);
}

int(0)
string(1) "a"
int(1)
string(1) "b"
int(2)
string(1) "c"