Online PHP editor | output for vR6hB

@ 2022-01-01T15:54:29Z

<?php

$names = [
    'ab1 ab2', // becomes ba1 ba2
    'qwerty uçop', // becomes ytrewq poçu
    'q1werty% uio*pl', // becomes y1trewq% lpo*iu
    'Привет, мир!', // becomes тевирП, рим!
    'Hello, dear @user_non-name, congrats100 points*@!', // olleH, raed @eman_non-resu, stragnoc100 stniop*@!
    'a'
];

function swapLetterPositions($string): string {
    $result = [];
    foreach (explode(' ', $string) as $index => $word) {
        $result[$index] = '';
        $count = preg_match_all('/(\pL)|(.)/u', $word, $m, PREG_SET_ORDER);
        for ($i = 0, $j = $count; $i < $count; ++$i) {
            if (isset($m[$i][2])) { // immovable
                $result[$index] .= $m[$i][2]; // append to string
            } else {  // movable from front
                while (--$j >= 0) {
                    if (!isset($m[$j][2])) { // movable from back
                        $result[$index] .= $m[$j][1]; // append to string
                        break;
                    }
                }
            }
        }
    }
    return implode(' ', $result);
}

foreach ($names as $name) {
    echo "\"$name\" => \"" . swapLetterPositions($name) . "\"\n---\n";
}

Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.4, 8.3.6 - 8.3.27, 8.4.1 - 8.4.14: "ab1 ab2" => "ba1 ba2" --- "qwerty uçop" => "ytrewq poçu" --- "q1werty% uio*pl" => "y1trewq% lpo*iu" --- "Привет, мир!" => "тевирП, рим!" --- "Hello, dear @user_non-name, congrats100 points*@!" => "olleH, raed @eman_non-resu, stargnoc100 stniop*@!" --- "a" => "a" ---
Output for 8.3.5: Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0 "ab1 ab2" => "ba1 ba2" --- "qwerty uçop" => "ytrewq poçu" --- "q1werty% uio*pl" => "y1trewq% lpo*iu" --- "Привет, мир!" => "тевирП, рим!" --- "Hello, dear @user_non-name, congrats100 points*@!" => "olleH, raed @eman_non-resu, stargnoc100 stniop*@!" --- "a" => "a" ---

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