Creates a new map using a callable to determine which pairs to include.

Description

public Ds\Map Ds\Map::filter ([ callable $callback ] )

Parameters

callback

bool callback ( mixed $key , mixed $value )

Optional callable which returns TRUE if the pair should be included, FALSE otherwise.

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

Return Values

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

Examples

Example #1 Ds\Map::filter() example using callback function


<?php
$map = new \Ds\Map(["a", "b", "c", "d", "e"]);

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

The above example will output something similar to:

object(Ds\Map)#3 (3) {
  [0]=>
  object(Ds\Pair)#2 (2) {
    ["key"]=>
    int(0)
    ["value"]=>
    string(1) "a"
  }
  [1]=>
  object(Ds\Pair)#4 (2) {
    ["key"]=>
    int(2)
    ["value"]=>
    string(1) "c"
  }
  [2]=>
  object(Ds\Pair)#5 (2) {
    ["key"]=>
    int(4)
    ["value"]=>
    string(1) "e"
  }
}

Example #2 Ds\Map::filter() example without a callback function


<?php
$map = new \Ds\Map(["a" => 0, "b" => 1, "c" => true, "d" => false]);

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

The above example will output something similar to:

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