Question

I have a form with a fairly large amount of input that will also be high traffic.
I declare $_SESSION vars so that on validation fails data that passes doesnt have to be rewritten out of convience to the user.

After I validate my form input like this:

$hey = htmlspecialchars($_POST['hey']);

if( correct_value($hey) == TRUE ) {
    $_SESSION['hey'] = $hey; 
}

I now have two variables with the same value in the same method where I update the db etc.

My question, is it faster from then on within the method to work with a:

$hey; //regular variable

Or a:

$_SESSION['hey']; //session variable

Is there a difference in performance? At high volumes does one perform faster than the other?

Answer 1

I haven’t done any benchmarks on this, but I strongly suspect that $_SESSION[] will always be a little slower than normal variables for writes, because it’s backed by the filesystem or database. Even if all $_SESSION[] storage is cached, there will still be more CPU and memory activity involved in using it than in using variables that are only held locally. For reads, there will still likely be a small difference, but it’ll be negligible compared to other factors.

So the comment above is right on the money. You have other areas of optimization that are more important than this one.

If you’re looking to improve performance, consider duplicating some of your input validation in JavaScript. (Don’t REPLACE server-side validation, as JS is not universal; just consider ways to avoid requiring it if possible.)