PHP マニュアル: Creates a new sequence using a callable to determine which values to include

説明

abstract public Ds\Sequence Ds\Sequence::filter(callable $callback = ?)

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

パラメータ

callback

bool callback(mixed $value)

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.

戻り値

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

例

例1 Ds\Sequence::filter example using callback function

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

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

上の例の出力は、たとえば以下のようになります。

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

例2 Ds\Sequence::filter example without a callback function

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

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

上の例の出力は、たとえば以下のようになります。

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