PHP下划线在filename变量？

Question

Why is there an underscore for data_?

Is there a simpler way of writing this, so that it makes more sense in terms of code readability?

My analysis:

data_ is supposed to take whatever data_ is, request a message via the variable postmessage from the form and make sure it's text and concatenate all this:

 $filename = 'data_'.$_REQUEST['postmessage'].'.txt';

I am a beginner and my analysis of this code could be wrong, but I am willing to learn from my mistakes.

Answer 1

Let's break it down a bit:

1. $filename = - assigning a value into a variable called $filename.
2. data_ - just a string.
3. $_REQUEST['postmessage'] - the value of the postmessage request parameter (could be either POST, GET or a COOKIE parameter. Try not using $_REQUEST too often, unless you absolutely have to. Use $_GET or $_POST instead). This would come from your form (as you've mentioned).
4. .'.txt' - just a string.

A dot between the elements above is used to concatenate the strings.

About your comment "and make sure it's text" - wrong. It doesn't make sure it's text. You need to make sure of that yourself and you probably should (for security reasons).