PHP - Ds Map::reverse() Function

The PHP Ds\Map::reverse() function reverses the order of the elements in the map in-place. The term in-place means that it modifies the original map without creating or storing any new memory.

Reversing an order of elements in a map means that the first element will be placed at the last position and the last element at the first. For example, if the map is ([1, 2]), the reverse map will be ([2, 1]).

Syntax

Following is the syntax of the PHP Ds\Map::reverse() function −

public Ds\Map::reverse(): void

Parameters

This function does not accept any parameter.

Return value

This function does not return any value but reverses the map elements' order.

Example 1

The following is the basic example of the PHP Ds\Map::reverse() function −

<?php 
   $map = new \Ds\Map([1, 2, 3]); 
   echo "The original map elements are: \n";
   print_r($map);
   echo "The map elements are reversing: \n";
   #using reverse() function
   $map->reverse();
   print_r($map);
?>

Output

The above program produces the following output −

The original map elements are:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 0
            [value] => 1
        )

    [1] => Ds\Pair Object
        (
            [key] => 1
            [value] => 2
        )

    [2] => Ds\Pair Object
        (
            [key] => 2
            [value] => 3
        )

)
The map elements are reversing:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 2
            [value] => 3
        )

    [1] => Ds\Pair Object
        (
            [key] => 1
            [value] => 2
        )

    [2] => Ds\Pair Object
        (
            [key] => 0
            [value] => 1
        )

)

Example 2

Following is another example of the PHP Ds\Map::reverse() function. We use this function to reverse the order of this map (["Tutorials", "Point", "India"]) elements −

<?php 
   $map = new \Ds\Map(["Tutorials", "Point", "India"]);
   echo "The map elements before reversing: \n";
   foreach($map as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
   echo "The map elements after reversing: \n";
   #using reverse() function
   $map->reverse();
   foreach($map as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
?>

Output

After executing the above program, it will generate the following output −

The map elements before reversing:
[0] = Tutorials
[1] = Point
[2] = India
The map elements after reversing:
[2] = India
[1] = Point
[0] = Tutorials