如何使用PHP在字符串中排列数据

<?php
$str = "Hello World";
$chars = str_split($str);
shuffle($chars);
$shuffledStr = implode('', $chars);
echo $shuffledStr;
?>

<?php
$str = "Hello World";
$shuffledStr = substr_shuffle($str);
echo $shuffledStr;
?>

<?php
$str = "Hello World";
$shuffledStr = str_shuffle($str);
echo $shuffledStr;
?>

<?php
function permute(&$arr, $l, $r) {
    if ($l == $r) {
        echo implode('', $arr) . "\n";
    } else {
        for ($i = $l; $i <= $r; $i++) {
            list($arr[$l], $arr[$i]) = array($arr[$i], $arr[$l]);
            permute($arr, $l + 1, $r);
            list($arr[$l], $arr[$i]) = array($arr[$i], $arr[$l]); // backtrack
        }
    }
}

$str = "abc";
$arr = str_split($str);
permute($arr, 0, count($arr) - 1);
?>