function insertion_sort($arr){
$size = count($arr);
for ($i = 1; $i < $size; $i++) {
$key = $arr[$i];
$j = $i-1;
while ($j >= 0 && $arr[$j] > $key) {
$arr[$j + 1] = $arr[$j];
$j = $j - 1;
}
$arr[$j + 1] = $key;
}
}