Creates a new vector using a callable to determine which values to include

# Ds\Vector::filter

(PECL ds >= 1.0.0)

Ds\Vector::filter — Creates a new vector using a callable to determine which values to include

### 说明

public function Ds\Vector::filter(callable `$callback` = ?): Ds\Vector

Creates a new vector using a callable to determine which values to include.

### 参数

`callback`

  function callback(mixed `$value`): bool

  Optional callable which returns `true` if the value should be included, `false` otherwise.

  If a callback is not provided, only values which are `true` (see converting to boolean) will be included.

### 返回值

A new vector containing all the values for which either the `callback` returned `true`, or all values that convert to `true` if a `callback` was not provided.

### 示例

示例 #1 Ds\Vector::filter() example using callback function

    <?php
    $vector = new \Ds\Vector([1, 2, 3, 4, 5]);

    var_dump($vector->filter(function($value) {
        return $value % 2 == 0;
    }));
    ?>

以上示例的输出类似于：

    object(Ds\Vector)#3 (2) {
      [0]=>
      int(2)
      [1]=>
      int(4)
    }

示例 #2 Ds\Vector::filter() example without a callback function

    <?php
    $vector = new \Ds\Vector([0, 1, 'a', true, false]);

    var_dump($vector->filter());
    ?>

以上示例的输出类似于：

    object(Ds\Vector)#2 (3) {
      [0]=>
      int(1)
      [1]=>
      string(1) "a"
      [2]=>
      bool(true)
    }

`↑` and `↓` to navigate • `Enter` to select • `Esc` to close • `/` to open