PHP - Sumas consecutivas con array

$a = "SELECT x FROM y";

    $b=$cn->query($a);

        while ($arraylist = $b->fetch_array()) {

            echo $arraylist[0]."</br>";

        }

for  ($i=0;$i<count($arraylist);$i++) {

    nuevo = 0;

    for ($j=0;$j<$i;$j++) {

        $nuevo += $arraylist[$j];

    }

    $arraylist[$i] = $nuevo;

}

$array = array(1, 2, 3, 4, 5);

$sum = 0;

foreach ($array as $value) {

    $sum += $value;

    echo $sum."</br>";

}

$a = "SELECT x FROM y";

    $b=$cn->query($a);

    $sum = 0;

        while ($arraylist = $b->fetch_array()) {

            $sum += $arraylist[0];

            echo $sum."</br>";

        }