<?php
$char = array(2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g','h','j','k','m','n','p','q','r','s','t','u','v','w','x','y','z');
 
$str1 = "00101";
$str2 = "00001";
$str = sprintf("%05d",$str1) . sprintf("%05d",$str2);
$val = ltrim($str, "0");
$val = encode($val, $char);
$val2 = decode($val, $char);
 
function encode($val, $char){
    $result = "";
    $base = count($char);
 
    while($val > 0){
        $result = $char[ fmod($val, $base) ] . $result;
        $val = floor($val / $base);
    }
 
    return ($result == "" ) ? 0 : $result;
}
 
function decode($str, $char){
    $result = 0;
    $base = count($char);
    $table = array_flip($char);
echo implode(",", $table) . "\n";
    $digit = array_reverse(preg_split('//', $str, -1, PREG_SPLIT_NO_EMPTY));
 
    foreach($digit as $i => $value){
        if(!isset($table[$value])) return false;
        $result += pow($base, $i) * $table[$value];
    }
 
    return $result;
}
 

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