My Hash PHP Class

Hash.php

<?php
/**
 * 
 */
class Encryption
{
    public function mt_rand_str($l, $c = 'abcdefghijklmnopqrstuvwxyz1234567890')
    {
        for ($s = '', $cl = strlen($c)-1, $i = 0; $i < $l; $s .= $c[mt_rand(0, $cl)], ++$i);
        return $s;
    }
    public function encrypt($txt, $key = 'anihc ctI')
    {
        $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
        $ikey ="-x6g6ZWm2G9g_vr0Bo.pOq3kRIxsZ6rm";
        $nh1 = rand(0,64);
        $nh2 = rand(0,64);
        $nh3 = rand(0,64);
        $ch1 = $chars[$nh1];
        $ch2 = $chars[$nh2];
        $ch3 = $chars[$nh3];
        $nhnum = $nh1 + $nh2 + $nh3;
        $knum = 0;$i = 0;
        while(isset($key[$i])) $knum +=ord($key[$i++]);
        $mdKey = substr(md5(md5(md5($key.$ch1).$ch2.$ikey).$ch3),$nhnum%8,$knum%8 + 16);
        $txt = base64_encode($txt);
        $txt = str_replace(array('+','/','='),array('-','_','.'),$txt);
        $tmp = '';
        $j=0;$k = 0;
        $tlen = strlen($txt);
        $klen = strlen($mdKey);
        for ($i=0; $i<$tlen; $i++) {
            $k = $k == $klen ? 0 : $k;
            $j = ($nhnum+strpos($chars,$txt[$i])+ord($mdKey[$k++]))%64;
            $tmp .= $chars[$j];
        }
        $tmplen = strlen($tmp);
        $tmp = substr_replace($tmp,$ch3,$nh2 % ++$tmplen,0);
        $tmp = substr_replace($tmp,$ch2,$nh1 % ++$tmplen,0);
        $tmp = substr_replace($tmp,$ch1,$knum % ++$tmplen,0);
        return $tmp;
    }
    public function decrypt($txt, $key = 'anihc ctI')
    {
        $chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
        $ikey ="-x6g6ZWm2G9g_vr0Bo.pOq3kRIxsZ6rm";
        $knum = 0;$i = 0;
        $tlen = strlen($txt);
        while(isset($key[$i])) $knum +=ord($key[$i++]);
        $ch1 = $txt[$knum % $tlen];
        $nh1 = strpos($chars,$ch1);
        $txt = substr_replace($txt,'',$knum % $tlen--,1);
        $ch2 = $txt[$nh1 % $tlen];
        $nh2 = strpos($chars,$ch2);
        $txt = substr_replace($txt,'',$nh1 % $tlen--,1);
        $ch3 = $txt[$nh2 % $tlen];
        $nh3 = strpos($chars,$ch3);
        $txt = substr_replace($txt,'',$nh2 % $tlen--,1);
        $nhnum = $nh1 + $nh2 + $nh3;
        $mdKey = substr(md5(md5(md5($key.$ch1).$ch2.$ikey).$ch3),$nhnum % 8,$knum % 8 + 16);
        $tmp = '';
        $j=0; $k = 0;
        $tlen = strlen($txt);
        $klen = strlen($mdKey);
        for ($i=0; $i<$tlen; $i++) {
            $k = $k == $klen ? 0 : $k;
            $j = strpos($chars,$txt[$i])-$nhnum - ord($mdKey[$k++]);
            while ($j<0) $j+=64;
            $tmp .= $chars[$j];
        }
        $tmp = str_replace(array('-','_','.'),array('+','/','='),$tmp);
        return trim(base64_decode($tmp));
    }
}

/* How to use Class */
$hash = new Encryption();
$setKey = "xyz";
$txt = "What you want to encrypt";
echo $hash->encrypt($txt, $setKey); // Ouput: Encrypt text
// replace ->encrypt($txt, $setKey) with ->decrypt($txt, $setKey)