Compress integer to string

integer_compress.php

<?php
// $codeset="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
$codeset="QybVileI4aZC7PMk9v85EcA0GS63oOqfKLmpJurNHstYhgBdjTUxWD2FRw1znX";
$base = strlen($codeset);

function intToStr($n)
{
    global $codeset, $base;
    $converted = "";
    
    while ($n > 0) {
      $converted = substr($codeset, ($n % $base), 1) . $converted;
      $n = floor($n/$base);
    }
    
    return $converted;
}

function strToInt($converted)
{   
    global $codeset, $base;
    $c = 0;
    for ($i = strlen($converted); $i; $i--) {
      $c += strpos($codeset, substr($converted, (-1 * ( $i - strlen($converted) )),1)) 
            * pow($base,$i-1);
    }
    return $c;
}

echo intToStr(1337);
echo ' ';
echo strToInt(intToStr(1337));