title: Testing for security vulnerabilities in web applications: Best practices?
body: <p>I'm developing a web application. Like, a proper one, I've used things like Joomla in the past to make awesome stuff but have now finally got my hands dirty with PHP, MySQL and CodeIgniter.</p>
  
  <p>When you're making serious web apps that'll handle large amounts of data, what precautions should I take against my data inputs to fully sanitise it? I know there's the obvious trim, escaping, xss cleaning, etc - but what other techniques should I incorporate to stop injections into the database?</p>
  
  <p>Not only that, but is there any non-destructive database injection code I can test all my inputs with? As in, it'll inject something visibile, but not actually do any harm to my test database? I'm not exactly a hacker and need a bit of guidance on this.</p>
  
  <p>What other common methods do hackers use to either destroy or read user's data, and how can I check for this myself? I don't have the money to hire a security consultant since I'm only 16 but have good experience with computers and I'm sure I could pull off a few tricks if given some hints as to what they are.</p>
  
  <p>I know that's a whole load of questions but to summarise, what do you do to make sure everything is 100% secure?</p>