The biggest I've started was a forum back when I was a newbie, that ended very badly.

The biggest I've ever seen though was a flight logging software with advanced graphing and paid subscription options. The site no longer exists, apparently the guys business plan didn't work.

The biggest non-php project I've done was a secure messaging and file transfer program for a the mortgage banker I work for. I would show you it but I would be fired for it.

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