Error Call to a member function move() on null code example

Example: Call to a member function move() on string

if ($request->hasFile('file')) {
    $destinationPath = 'path/th/save/file/';
    $files = $request->file('file'); // will get all files

    foreach ($files as $file) {//this statement will loop through all files.
        $file_name = $file->getClientOriginalName(); //Get file original name
        $file->move($destinationPath , $file_name); // move files to destination folder
    }
}