php foreach与数组和对象，并重新定义它们的价值

Question

I'm trying to foreach through an array of objects inside an array. I'm not receiving errors, but it seems not to be storing the new value I'm trying to establish. I've found many answers on here closely related to this question, but I'm not understanding, and I'm hoping someone can make this clearer.

Essentially, this converts kg to lbs.

    $kg_conv = 2.20462262;
    $weights = array($data['progress']->weight, $data['progress']->squats,
    $data['progress']->bench, $data['progress']->deadlift); 

    foreach ($weights as $value) {
        $value = $value * $kg_conv;
    }

The values in the array come out unchanged. From what I've read, I should be using $data['progress'] and iterating through that, but I'm not understanding how to refer to only some of the elements inside instead of all of them. I also tried cutting out some redundancy by storing the objects in $progress instead of $data['progress'] but still not success.

UPDATE: The following has not worked

1

    foreach ($weights as &$value) {
        $value = $value * $kg_conv;
    }

2

    foreach ($weights as $key => &$value) {
        $value = $value * $kg_conv;
    }

3

    foreach ($weights as $key => $value) {
        $weights[$key] = $value * $kg_conv;
    }

Answer 1

it does not work because you do not modify data array, you only modify copy made from this array, which is another array in memory

Solution: (will work for object's fields too)

$kg_conv = 2.20462262;
$weights = ['weight', 'squats','bench', 'deadlift']; 

foreach ($data['progress'] as $key=>&$value) {
  if ( in_array($key,$weights)
    $value = $value * $kg_conv;
}