Secure highScores

I am to make a game ... and some friends are working on a website where the game will be hosted among other stuff. The highest score of the game will win ... something.

I'm very new to anything that involves web-development so I have the following question.

How I secure the High-score so the user cannot modify it ? Can it be done from Construct2 or ... can it be done at all ?

Thank you in advance.

For starters: take a look here for an excellent tutorial on MySQL/PHP integration with a game:

http://www.scirra.com/tutorials/346/online-high-score-table-ajax-php-mysql/page-1

Security is not integrated into this solution, but if you read further into standard encryption functionality in PHP (google it) you should be able to get a secure solution that you're after.