strpos(): Argument #1 ($haystack) must be of type string, array given

laravel laravel-8 strpos php-8

PHP Snippet 1:

Route::get('posts/{post}', function ($slug) {
    $post = Post::find($slug);

    return view('post', [
        'post' => $post
    ]);

})
    ->where('post', '[A-z_-]+');

PHP Snippet 2:

php8.0-mbstring & php8.0-xml