Example of permutations

permutations_example.php

<?php
//https://www.geeksforgeeks.org/write-a-c-program-to-print-all-permutations-of-a-given-string/

function swap(string &$str, int $i, int $ii) : void {
    $tmp = $str[$i];
    $str[$i] = $str[$ii];
    $str[$ii] = $tmp;
}

function permute(string $str, int $l, int $r, array &$result) : void { 
    if ($l == $r) 
        $result[] = $str;
    else { 
        for ($i = $l; $i <= $r; $i++) { 
            swap($str, $l, $i); 
            permute($str, $l + 1, $r, $result); 
            swap($str, $l, $i); 
        } 
    } 
} 
  
$str = "ABC"; 
$result = [];
$n = strlen($str) - 1;
permute($str, 0, $n, $result); 
var_dump($result);