Removes and returns the first value

# Ds\Sequence::shift

(PECL ds >= 1.0.0)

Ds\Sequence::shift — Removes and returns the first value

### 说明

abstract public function Ds\Sequence::shift(): mixed

Removes and returns the first value.

### 参数

此函数没有参数。

### 返回值

The first value, which was removed.

### 错误／异常

UnderflowException if empty.

### 示例

示例 #1 Ds\Sequence::shift() example

    <?php
    $sequence = new \Ds\Vector(["a", "b", "c"]);

    var_dump($sequence->shift());
    var_dump($sequence->shift());
    var_dump($sequence->shift());
    ?>

以上示例的输出类似于：

    string(1) "a"
    string(1) "b"
    string(1) "c"

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