PHP - Ds Sequence::sort() Function

The PHP Ds\Sequence::sort() function is used to sort the elements of a sequence in-place. The term "in-place" means that the function sorts the elements within the existing sequence without allocating additional memory for a new sequence.

By default, the elements are sorted in "ascending" order. However, you can provide an optional comparator function to sort the sequence in a custom order, such as descending order.

Syntax

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

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

Parameters

Following is the parameter of this function −

• comparator − A comparison function compares elements and must return 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 comparator function is omitted, the Ds\Sequence::sort() function sorts the sequence elements in ascending order by default as follows:

<?php 
   $seq = new \Ds\Vector([2, 7, 1, 9, 6, 3]); 
   echo "The original sequence: \n";
   print_r($seq);
   echo "The sequence after sort: \n";
   #using sort() function
   $seq->sort();
   print_r($seq); 
?>

Output

The above program produces the following output −

The original sequence:
Ds\Vector Object
(
    [0] => 2
    [1] => 7
    [2] => 1
    [3] => 9
    [4] => 6
    [5] => 3
)
The sequence after sort:
Ds\Vector Object
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 6
    [4] => 7
    [5] => 9
)

Example 2

Following is another example of the PHP Ds\Sequence::sort() function. We use this function to sort the current sequence ([3, 5, 11, 2, 6, 1, 4, 9]) elements in descending order using the comparator function −

<?php 
   $seq = new \Ds\Vector([3, 5, 11, 2, 6, 1, 4, 9]);
   echo "The sequence before sorting: \n";
   print_r($seq);
   #using sort() function
   $seq->sort(function($x, $y) { 
      return $y <=> $x; #sorting in descending order
   }); 
   echo "The sequence after sorting: \n";
   print_r($seq);
?>

Output

After executing the above program, the following output will be displayed −

The sequence before sorting:
Ds\Vector Object
(
    [0] => 3
    [1] => 5
    [2] => 11
    [3] => 2
    [4] => 6
    [5] => 1
    [6] => 4
    [7] => 9
)
The sequence after sorting:
Ds\Vector Object
(
    [0] => 11
    [1] => 9
    [2] => 6
    [3] => 5
    [4] => 4
    [5] => 3
    [6] => 2
    [7] => 1
)