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:Â
php
<?php // PHP program to illustrate the filter() // function of Ds\map Â
// Creating a Map $map = new \Ds\Map([    1 => "Welcome",    2 => "to",    3 => "Geeks",     4 => "for",    5 => "Geeks"]);             Â
// Display new sequence using filter function var_dump($map->filter(function($key, $val) { Â Â Â Â return $key % 3 == 0; })); Â
?> |
Output:
object(Ds\Map)#3 (1) {
[0]=>
object(Ds\Pair)#2 (2) {
["key"]=>
int(3)
["value"]=>
string(5) "Geeks"
}
}
Program 2:Â
php
<?php // PHP program to illustrate the filter() // function of Ds\map Â
// 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; })); Â
?> |
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)
}
}
