Encoding/Decoding Integer or String

convert.php

<?php

/**
 * Encode/Decode a string/integer
 * 
 * @author CarcaBot
 *
 * @param string $text
 * @return string
 */
function mb_str_split($string) { // used for utf8 strings
# Split at all position not after the start: ^
# and not before the end: $
    return preg_split('/(?<!^)(?!$)/u', $string);
}

function encode($str = "") {
    $string = "";

    foreach (mb_str_split($str) as $char) {

        $b = ord($char);
        if ($b >= 97 && $b <= 109 || $b >= 65 && $b <= 77) {
            $b += 13;
        } elseif ($b >= 110 && $b <= 122 || $b >= 78 && $b <= 90) {
            $b -= 13;
        }

        $string .= chr($b);
    }

    return $string;
}

function decode($str = "") {
    return encode($str);
}

$str = "SecretWord";
$encoded = encode($str);
$decoded = decode($str);
echo sprintf("Encoded: %s \r\n<br/>Decoded: %s", encode($str), decode($encoded));

/*
result:
Encoded: FrpergJbeq 
Decoded: SecretWord
*/

convert.vb

    'Encode/Decode a string/integer
    '@author CarcaBot
    '@param string $text
    '@return string

    Public Shared Function encode(ByVal Text As String) As String

        Dim Buffer As New System.Text.StringBuilder

        For Each C As Char In Text

            Dim B As Integer = Microsoft.VisualBasic.AscW(C)

            If B >= 97 And B <= 109 Or B >= 65 And B <= 77 Then
                B += 13
            ElseIf B >= 110 And B <= 122 Or B >= 78 And B <= 90 Then
                B -= 13
            End If

            Buffer.Append(Microsoft.VisualBasic.ChrW(B))

        Next
        Return Buffer.ToString
    End Function
    
Public Shared Function decode(ByVal Text As String) As String
    return encode(Text)
End Function