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We can use validation to ensure that the data received from a user's form submission is within the allowable guidelines determined in our code.
This is to say that we could set a text field to be no fewer than 20 characters, or a datetime field should be in the future, or that a checkbox must be checked... Symfony comes preconfigured with a large number of Validation Constraints, and I'd advise keeping this handy reference close to hand.
Some good validation techniques are: When to Use Regular Expressions I often see what I would call an overuse of regular expressions.
You should understand that regular expressions require extra processing, so they shouldn't be used flippantly.
A regular expression that allows for any valid comment or address would allow for just about anything.If you have a form where the user can submit various data, don't assume anything about it. The most common security problem is the so-called SQL injections, where a malicious visitor injects SQL into your database queries, allowing him to e.g. The most common way of doing this is either through the query string (the page address) or through a form.In a later chapter, I will show you why SQL injections can be so dangerous, but for now, we will look at another danger when trusting the user data too much.We want to change that now to stop situations where bad or invalid data might find its way into our database.
If we are using Twig - as we are in this series - then when we render out a Symfony form from our controller action, then depending on the field types you use, you may get some HTML 5 inputs / form fields in your form. Inside our database this would be a plain old string, but in our application we really need to ensure that it looks and feels like an email. The key point here is that these rules are only enforced on the client / users browser.
You likely don't need to be told that this is exactly the sort of thing your boss / clients will get quite upset about, especially if it takes a while for this problem to be noticed.