share-online.biz file size encryption algorithm

share-online.biz.php

<?php
function encrypt($original) {
    $arr = range(0, strlen($original) - 1);
    shuffle($arr);
    $shuffleStr = '';
    $hexStr = '';
    foreach ($arr as $char) {
        $shuffleStr .= $original[$char];
        $hexStr .= str_pad(dechex($char), 3, "0", STR_PAD_LEFT);
    }
    $str = strrev($shuffleStr . 'a|b' . $hexStr);
    return $str;
}
function info($a) {
    $a = strrev($a);
    $a = explode('a|b', $a);
    $a[1] = str_split($a[1], 3);
    $b = [];
    for ($i=0; $i < count($a[1]); $i++) {
        $a[1][$i] = hexdec($a[1][$i]);
        $b[$a[1][$i]] = $i;
    }
    $a[1] = "";
    for ($i=0; $i < count($b); $i++) {
        if (isset($a[0][$b[$i]])) {
            $a[1] = $a[1].$a[0][$b[$i]];
        } else {
            $a[1] .= " ";
        }
    }
    return $a[1];
}

$encryptedStr = encrypt('thisiscleanstring,nothingheree');
$decryptedStr = info($encryptedStr);

echo 'Encryped String: ' . $encryptedStr . "\n";
echo 'Decryped String: ' . $decryptedStr . "\n";