<?php

    function NPHencode($strPlaintext)
    {
        $strPlaintextAlphaOnly = preg_replace("[\W]", "", $strPlaintext);
        $strCiphertextAlphaOnly = "";
        for ($i = 0; $i < strlen($strPlaintextAlphaOnly); $i += 2)
        {
            $strCiphertextAlphaOnly .= $strPlaintextAlphaOnly[$i];
        }
        $strCiphertextAlphaOnlyTail = "";
        for ($i = 1; $i < strlen($strPlaintextAlphaOnly); $i += 2)
        {
            $strCiphertextAlphaOnlyTail = $strPlaintextAlphaOnly[$i] . $strCiphertextAlphaOnlyTail;
        }
        $strCiphertextAlphaOnly .= $strCiphertextAlphaOnlyTail;
        $strCiphertext = "";
        $padcount = 0;
        for ($i = 0; $i < strlen($strPlaintext); $i++)
        {
            if (preg_match("[\W]", substr($strPlaintext, $i, 1)))
            {
                $strCiphertext .= substr($strPlaintext, $i, 1);
                $padcount++;
            }
            else
            {
                $strCiphertext .= substr($strCiphertextAlphaOnly, $i-$padcount, 1);
            }
        }
        return($strCiphertext);
    }

    function NPHdecode($strCiphertext)
    {
        $strCiphertextAlphaOnly = preg_replace("[\W]", "", $strCiphertext);
        $strPlaintextAlphaOnly = "";
        for ($i = 0; $i < strlen($strCiphertextAlphaOnly); $i++)
        {
            if (floor($i/2) == $i/2)
            {
                $strPlaintextAlphaOnly .= substr($strCiphertextAlphaOnly, $i/2, 1);
            }
            else
            {
                $strPlaintextAlphaOnly .= substr($strCiphertextAlphaOnly, floor($i/-2), 1);
            }
        }
        $strPlaintext = "";
        $padcount = 0;
        for ($i = 0; $i < strlen($strCiphertext); $i++)
        {
            if (preg_match("[\W]", substr($strCiphertext, $i, 1)))
            {
                $strPlaintext .= substr($strCiphertext, $i, 1);
                $padcount++;
            }
            else
            {
                $strPlaintext .= substr($strPlaintextAlphaOnly, $i-$padcount, 1);
            }
        }
        return($strPlaintext);
    }

?>