PHP - Ds Map::sort() Function

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The PHP Ds\Map::sort() function is used to sort the elements of the map in-place in ascending order by default. The term in-place means that it modifies the original map without creating or storing any new memory.

This function accepts an optional parameter using which you can specify the criteria based on the return value the element in the map will be sorted.

Below are the lists of some important points of the comparator function −

• It returns -1, if the first element is greater than the second element.
• It returns 1, if the first element is less than the second element.
• It returns 0, if the first element is equal to the second element.

Syntax

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

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

Parameters

Following is the parameter of this function −

• comparator (optional) − An optional comparator function compares the elements and returns an integer value.

Following is the syntax of the comparator function −

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

Return value

This function does not return any value.

Example 1

If the optional comparator function is omitted, this function sorts the elements in an ascending order.

The following program demonstrates the usage of the PHP Ds\Map::sort() function −

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

Output

The above program produces the following output −

The map elements before sorting:
Ds\Map Object
(
    [0] => Ds\Pair Object
        (
            [key] => 0
            [value] => 20
        )

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

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

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

    [1] => Ds\Pair Object
        (
            [key] => 0
            [value] => 20
        )

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

)

Example 2

If we pass the comparator function as an argument to the PHP Ds\Map::sort() function, the element will be sorted according to the specified comparator function's condition −

<?php 
   $map = new \Ds\Map([5, 1, 4, 3, 2]);
   echo "The map elements before sorting: \n";
   foreach($map as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
   $func = function($first, $second) { 
      if($first > $second) 
         return -1; 
      else if($first < $second) 
         return 1;
      else 
         return 0;
   }; 
   $map->sort($func); 
   echo "The map elements before sorting: \n";
   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 before sorting:
[0] = 5
[1] = 1
[2] = 4
[3] = 3
[4] = 2
The map elements before sorting:
[0] = 5
[2] = 4
[3] = 3
[4] = 2
[1] = 1

Example 3

Let's try to sort the elements of the map which contain the character values (['a', 'i', 'u', 'o', 'e']) without using the comparator function.

<?php 
   $map = new \Ds\Map(['a', 'i', 'u', 'o', 'e']);
   echo "The map elements before sorting: \n";
   foreach($map as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   } 
   $map->sort(); 
   echo "The map elements before sorting: \n";
   foreach($map as $key=>$value){
	   echo "[".$key."] = ".$value."\n";
   }
?>

Output

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

The map elements before sorting:
[0] = a
[1] = i
[2] = u
[3] = o
[4] = e
The map elements before sorting:
[0] = a
[4] = e
[1] = i
[3] = o
[2] = u