PHP | Ds\Map filter() Function

The Ds\Map::filter() function is an inbuilt function in PHP which is used to create a new map using the filter function.

Syntax:

Ds\Map public Ds\Map::filter( $callback )

Parameters: It contains a single parameter $callback which is an optional parameter and it returns True if the value should be included, False otherwise.

Return value: This function returns 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.

Below programs illustrate the Ds\Map::filter() function in PHP:

Program 1:

<?php
// PHP program to illustrate the filter()
// function of Ds\map

// Creating a Map
$map = new \Ds\Map([
    1 => "Welcome",
    2 => "to",
    3 => "Geeks",
    4 => "for",
    5 => "Geeks"]);


// Display new sequence using filter function
var_dump($map->filter(function($key, $val) {
    return $key % 3 == 0;
}));

?>

Output:

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

Program 2:

<?php
// PHP program to illustrate the filter()
// function of Ds\map

// Creating a Map
$map = new \Ds\Map([
        1 => 10,
        2 => 20,
        3 => 30,
        4 => 40,
        5 => 50]);

// Display new sequence using filter function
var_dump($map->filter(function($key, $val) {
    return $val % 20 == 0;
}));

?>

Output:

object(Ds\Map)#3 (2) {
  [0]=>
  object(Ds\Pair)#2 (2) {
    ["key"]=>
    int(2)
    ["value"]=>
    int(20)
  }
  [1]=>
  object(Ds\Pair)#4 (2) {
    ["key"]=>
    int(4)
    ["value"]=>
    int(40)
  }
}

Reference: https://www.php.net/manual/en/ds-map.filter.php