PHP | Ds\Map filter() Function

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

 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 
// 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 
// 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