在php文件中重新声明类，现在生成了一个函数

有一个文件myclass.php:

<?php
class Myclass {
    public static function Fun1() {
    }
}

和我试着做一个自己的框架，在那里使用代码生成:

$class = "MyClass";
$function = "Fun1";
$fname = "myclass.php"
if (class_exists($class) && !method_exists($class, $functionName)) {
    $current = file_get_contents($fname);
    if ($current) {
        $strIndex = strlen($current);
        while ($strIndex-- && $current[$strIndex] != "}");//removing the last '}'
        $current = substr($current, 0, $strIndex);
        $current .= "'tpublic static function $functionName() {'n";//there inserting the new function
        $current .= "'n";
        $current .= "'t}'n";
        $current .= "}'n";
        $current .= "'n";
        file_put_contents($fname, $current);
        require $fname;//I load the file again, but how to redeclare the class?
    }
}

. .和我得到一个消息:致命错误:不能重新声明类MyClass在C:'xampp'htdocs'myproj'index.php在第12行。谢谢你。