Checkbox preset ud fra array

<?php
if (isset($_GET['foo'])) {
    $bar = array_sum($_GET['foo']);
   
    echo '$bar contains the number: ' . $bar . '<br>';
   
    if ($bar & 1) echo 'Box #1 was checked<br>';
    if ($bar & 2) echo 'Box #2 was checked<br>';
    if ($bar & 4) echo 'Box #3 was checked<br>';
    if ($bar & 8) echo 'Box #4 was checked<br>';
    if ($bar & 16) echo 'Box #5 was checked<br>';
    if ($bar & 32) echo 'Box #6 was checked<br>';
    if ($bar & 64) echo 'Box #7 was checked<br>';
    if ($bar & 128) echo 'Box #8 was checked<br>';
}
?>

<form action="">
    1: <input value="1" name="foo[]" type="checkbox"><br>
    2: <input value="2" name="foo[]" type="checkbox"><br>
    3: <input value="4" name="foo[]" type="checkbox"><br>
    4: <input value="8" name="foo[]" type="checkbox"><br>
    5: <input value="16" name="foo[]" type="checkbox"><br>
    6: <input value="32" name="foo[]" type="checkbox"><br>
    7: <input value="64" name="foo[]" type="checkbox"><br>
    8: <input value="128" name="foo[]" type="checkbox">

    <p><button type="submit">TEST</button></p>
</form>