Php restricting the data insertion in mysql

I have a list box with two times i.e 12:00 to 2:00 and 2:00 to 4:00.I want to do that when someone submit the form (example a meeting reservation form) the tim开发者_StackOverflow社区ing inserted into the databse should be booked only for three times.when someone tries to insert the same time for the fourth time,it should give us message like (already booked). help me to do this in php, mysql. thanks

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There is no real question here, you should start the project and when you come up against a brick wall we can help you.

Here are some good resourcesL

Start by reading up on PHP - http://www.php.net

The mysql manual is also very helpful http://dev.mysql.com/doc/refman/5.1/en/manual-info.html