防止php注入[重复]

im looking for all the ways to prevent people from entering php code into text field at the php level. i have prevention from sql injection but do i not need a way to prevent people from say messing with my if statements?

$email=$_POST["email"];
if(filter_var($email, FILTER_VALIDATE_EMAIL))
{
    //do suff
}

can a user not enter something like "not@a@valid@email.com = valid@email.com" as the email and it will be considered valid. I know this example isn't bad for the server but i'm sure others and come up with more deadly.

Or am i worrying about something that is never a problem?

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This is not a problem, since the user data is the value of a string. It's no different from saying:

filter_var("die()", FILTER_VALIDATE_EMAIL)

That also doesn't kill your program. It's just text.

Just don't use eval. Not ever, but specifically not ever on user input.