PHP マニュアル: Adds values to the front of the deque

public void Ds\Deque::unshift(mixed $values = ?)

Adds values to the front of the deque, moving all the current values forward to make room for the new values.

values

The values to add to the front of the deque.

注意:
Multiple values will be added in the same order that they are passed.

値を返しません。

例1 Ds\Deque::unshift example

<?php
$deque = new \Ds\Deque([1, 2, 3]);

$deque->unshift("a");
$deque->unshift("b", "c");

print_r($deque);
?>

上の例の出力は、たとえば以下のようになります。

Ds\Deque Object
(
    [0] => b
    [1] => c
    [2] => a
    [3] => 1
    [4] => 2
    [5] => 3
)