array_copy_and_modification.php

<?php

//$pattern = '/^(.*)\[(p|m|v)_(.*)\]/i';
//preg_match($pattern, '331-60905/5106[p_0].JPG', $matches);
//
//var_dump($matches);

$orig = [2.2, 2, 0.7];
$sQty = 4.2;
$new = array_fill(0, count($orig), 0);
$compare = 0;
foreach ($orig as $key => $item) {
    $compare += $item;
    if ($compare <= $sQty) {
        $new[$key] = $item;
    } else {
        $diff = $compare - $sQty;
        $new[$key] = $item - $diff;
        break;
    }
}
var_dump($new);