Question

How could I do something like this

$ranges = array(
    range(34, 37) => 'Group A',
    range(38, 39) => 'Group B',
    range(40, 41) => 'Group C',
);

foreach($ranges as $range_key => $range_value) {
    echo "K: ".$range_key." V: ".$range_value."\n";
}

I get

Warning: Illegal offset type

Answer 1

range() returns an array which cannot be used as an array key. You will need to use each value in the returned array as a key, like this:

foreach ( range(34, 37) as $value ) {
    $ranges[$value] = 'Group A';
}
foreach ( range(38, 39) as $value ) {
    $ranges[$value] = 'Group B';
}
foreach ( range(40, 41) as $value ) {
    $ranges[$value] = 'Group C';
}