Use of & in query strings

Question

I am following this tutorial about integrating Paypal in one's website.
Many times in the page, at line 20 of step 3 for example, I find this:

if (!isset($_POST["txn_id"]) && !isset($_POST["txn_type"])){  

I really don't understand the use of &in the query strings.
The language used is PHP/HTML

Answer 1

That's not intentionally kept by the developer. The & characters are converted into the & by some kind of plugin/scripts while formatting the code.

Looking at the code you should have this:

if (!isset($_POST["txn_id"]) && !isset($_POST["txn_type"])){ 

Answer 2

It's a problem in whatever software they're using to encode the text of the article. It's a good reason to preserve input text and encode for different contexts.

It should simply be && .

Answer 3

I don't know if you found a real solution but this chain is written in Wordpress documentation, here : https://developer.wordpress.org/themes/basics/including-css-javascript/

++ Nicolas.