PHP | ArrayIterator uksort() Function

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The ArrayIterator::uksort() function is an inbuilt function in PHP which is used to sort the keys by using a user-defined comparison function.

Syntax:

void ArrayIterator::uksort( callable $cmp_function )

Parameters: This function accepts single parameter $cmp_function which holds the user defined comparison function.

Return Value: This function does not return any value.

Below programs illustrate the ArrayIterator::uksort() function in PHP:
Program 1:

<?php 
  
// Declare an ArrayIterator 
$arrItr = new ArrayIterator( 
    array( 
        "a" => 4, 
        "b" => 2, 
        "g" => 8, 
        "d" => 6, 
        "e" => 1, 
        "f" => 9 
    ) 
); 
  
// User defined comparator function  
function sorting($a, $b) {  
    if($a == $b) 
        return 0;  
    return ($a < $b) ? -1 : 1;  
}  
  
$arrItr->uksort("sorting");  
    
// Printing the sorted array.  
print_r($arrItr);  
  
?> 

Output:

ArrayIterator Object
(
    [storage:ArrayIterator:private] => Array
        (
            [a] => 4
            [b] => 2
            [d] => 6
            [e] => 1
            [f] => 9
            [g] => 8
        )

)

Program 2:

<?php 
     
// Declare an ArrayIterator 
$arrItr = new ArrayIterator( 
    array( 
        "b" => "for", 
        "a" => "Geeks", 
        "e" => "Science", 
        "c" => "Geeks", 
        "f" => "Portal", 
        "d" => "Computer"
    ) 
); 
    
// Declare a comparison function to sort   
// values in descending order  
function comparison($val1, $val2) {  
    if ($val1 == $val2) {  
        return 0;  
    }  
    else if($val1 > $val2)  
        return -1;  
    else
        return 1;  
}  
    
$arrItr->uksort('comparison');  
    
// Print the sorted ArrayObject  
print_r($arrItr);  
  
?> 

Output:

ArrayIterator Object
(
    [storage:ArrayIterator:private] => Array
        (
            [f] => Portal
            [e] => Science
            [d] => Computer
             => Geeks
            [b] => for
            [a] => Geeks
        )

)

Reference: https://www.php.net/manual/en/arrayiterator.uksort.php

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