Validating parentheses for a MySQL query

I'm giving my users the ability to create their own MySQL queries. Don't worry, I'm taking all the sql injection etc into account.

What I am wanting to do is validate the parentheses they use while creating their query...

So lets say they their query looks like this:

$string = '1 AND (2 OR 3) AND (4 AND (5 OR 6)';

See how they开发者_运维问答 didn't close the open parenthesis before the number 4? Is there any regex I could run on this to validate any open or closed parentheses that haven't been added correctly?

I've been playing and searching everywhere but I have no idea how to make this work.

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Thanks @Jayantha! Here's the solution I found from clicking your link:

$string = '1 AND (2 OR 3) AND (4 AND (5 OR 6)';

if (!preg_match("/^((?:[^()]|\((?1)\))*+)$/", $string, $matches))
    echo 'Your parentheses are wrong!';