Returns the first value in the deque

# Ds\Deque::first

(PECL ds >= 1.0.0)

Ds\Deque::first — Returns the first value in the deque

### 说明

public function Ds\Deque::first(): mixed

Returns the first value in the deque.

### 参数

此函数没有参数。

### 返回值

The first value in the deque.

### 错误／异常

UnderflowException if empty.

### 示例

示例 #1 Ds\Deque::first() example

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

以上示例的输出类似于：

    int(1)

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