早上好，工程师们
此vb.net代码负责加密密码

Public Function Encrypt(ByVal clave As String) As String
        ' Defino variables
        Dim indice As Integer = 1
        Dim largo As Integer = 0
        Dim final As String = ""
        largo = Len(Trim(clave))
        Dim caracteres(largo) As String
        For indice = 1 To largo
            caracteres(indice) = Mid(clave, indice, 1)
            caracteres(indice) = Chr(Asc(caracteres(indice)) + indice)
            final = final & caracteres(indice)
        Next indice

        Return final
    End Function

这就是我用php编写的代码，但由于没有得到预期的结果，我在某些地方失败了

public static function encryption($clave){
            $indice = 0;
            $largo = 0;
            $final = '';

            $largo = strlen(trim($clave));
            $caracteres = array();
            for ($indice; $indice < $largo; $indice++) { 
                $caracteres[$indice] = substr($clave, $indice, 1);
                $caracteres[$indice] = chr(ord($caracteres[$indice]) + $indice);
                $final = $final.$caracteres[$indice];
            }
            return $final;
        }

例如，在vb.net中，12345密钥在2468中加密；在php中，相同的密钥在13579中加密
我将感谢所有能够帮助我发现我失败的地方以及如何弥补失败的人
谢谢