PHP - Ds Map::ksort() Function

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The PHP Ds\Map::ksort() function is used to sort the map keys in-place. The term "in-place" means that the sorting is done within the same map, without requiring any additional memory or creating a new map instead it directly modifies the original map.

The default sorting order of the keys is ascending. However, you can pass an optional comparison function that compares the arguments and returns an integer value less than, equal to, or greater than zero if the first argument is respectively less than, equal to, and greater than the second argument.

Syntax

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

public Ds\Map::ksort(callable $comparator = ?): void

Parameters

• comparator − An optional comparison function compares the specified arguments.

Following is the syntax of the comparator function −

callback(mixed $a, mixed $b): int

Return value

This function doesn't return any value.

Example 1

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

<?php  
   $map = new \Ds\Map([3 => 30, 1=> 10, 2 => 20]);
   echo "The map elements are: \n";
   print_r($map);
   echo "The map elements after key sort: \n";
   #using ksort() function
   $map->ksort();
   print_r($map);
?>

Output

The above program produces the following output −

The map elements are:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 3
            [value] => 30
        )

    [1] => Ds\Pair Object
        (
            [key] => 1
            [value] => 10
        )

    [2] => Ds\Pair Object
        (
            [key] => 2
            [value] => 20
        )

)
The map elements after key sort:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 1
            [value] => 10
        )

    [1] => Ds\Pair Object
        (
            [key] => 2
            [value] => 20
        )

    [2] => Ds\Pair Object
        (
            [key] => 3
            [value] => 30
        )

)

Example 2

If the key of the values in the map is not specified, the Ds\Map::ksort() function will not modify the original map, which will remain unchanged. This is because the default keys are already arranged in sorted ascending order −

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

Output

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

The map elements are:
[0] = Tutorials
[1] = Point
[2] = India
The map elements after key sort:
[0] = Tutorials
[1] = Point
[2] = India

Example 3

If an optional comparator function is provided, it compares the map elements and returns an integer value based on the comparison −

<?php  
   $map = new \Ds\Map([2 => 'a', 0 => 'b', 1 => 'c']);
   echo "The map elements are: \n";
   foreach($map as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
   echo "The map elements after key sort: \n";
   #using ksort() & comparator function
   $map->ksort(function($a, $b){
	   return $a$b;
   });
   foreach($map as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   } 
?>

Output

Once the above program is executed, it will display the following output −

The map elements are:
[2] = a
[0] = b
[1] = c
The map elements after key sort:
[0] = b
[1] = c
[2] = a