Question: I had made a java program in which it is supposed to take input from a user in a GUI frame and store in a .dat file in row and columns. The problem is with this particular code as it is not giving the desired results. the user should be able to enter only numbers between 20 to 30 using a keylistener. the input should not accept any number that is out of this range, i.e, 19 or 31. Eclipse is throwing an error 'invalid character constant'. Is there any way out?

```
// input validation that restricts user to enter specific number range between 20 and 30

txDeposit.addKeyListener(new KeyAdapter() {
    public void keyTyped(KeyEvent ke) {
        char c = ke.getKeyChar();
        if(!(ke.getKeyChar() >= '20' && ke.getKeyChar() <= '30')) {
            getToolkit().beep();
            ke.consume();
        }
    }
});

```

Answer: 
Your app.yaml file is for routing requests from incoming URLs to the initial script you want to use to process the request.

You don't need to add routings for each and every \*.php file that you want to include from one script to another.

For example, look at the [app.yaml](https://developers.google.com/appengine/articles/wordpress) example for running wordpress. It just has the URLs that clients will access, but not all of the php scripts used by wordpress.
The problem you face is most likely independent to Google App Engine. On Google App Engine, the [standard rules of PHP file-inclusion](http://php.net/include) still applies. The only potential difference here is that the files are read-only (but that should not pose any problems in your case).

So if `lib1.php` requires `lib2.php` you need to require the later before you require the other. That is standard PHP behavior:

```
require 'myfolder/folder/lib2.php'; 
require 'myfolder/folder/lib1.php';

```

To learn more what exactly caused the 500 error on Google App Engine, [consider downloading the log and look into it](https://developers.google.com/appengine/docs/php/tools/uploadinganapp#Downloading_Logs). This is also independent to Google App Engine, because that is the best suggestion one can give with any webserver on 500 errors.