The Ds\Deque::filter() function is an inbuilt function in PHP which is used to filter out the elements from the deque based on the operation defined in the callback function.
Syntax:
public Ds\Deque::filter( $callback ) : Ds\Deque
Parameters: This function accepts single parameter $callback which is the callback function which contains the definition of filter to the elements from the deque.
Return Value: This function returns a new Deque which contains all the values for which callback returns True or all values that convert to True if a callback was not provided.
Below programs illustrate the Ds\Deque::filter() function in PHP:
Program 1:
<?php   // Creating a deque $deque = new \Ds\Deque([1, 2, 3, 4, 5, 6]);   echo("Elements in the deque are\n");   print_r($deque);   // Use filter() function to filter // the elements as per requirement print_r($deque->filter(function($value) {     return $value % 2 == 0; }));   ?> |
Output:
Elements in the deque are
Ds\Deque Object
(
[0] => 1
[1] => 2
[2] => 3
[3] => 4
[4] => 5
[5] => 6
)
Ds\Deque Object
(
[0] => 2
[1] => 4
[2] => 6
)
Program 2:
<?php   // Creating a deque $deque = new \Ds\Deque([10, 20, 3, 40, 50, 6]);   echo("Elements in the deque are\n");   print_r($deque);   // Use filter() function to filter // the elements as per requirement print_r($deque->filter(function($value) {     return $value % 10 != 0; }));   ?> |
Output:
Elements in the deque are
Ds\Deque Object
(
[0] => 10
[1] => 20
[2] => 3
[3] => 40
[4] => 50
[5] => 6
)
Ds\Deque Object
(
[0] => 3
[1] => 6
)
Reference: http://php.net/manual/en/ds-deque.filter.php
