How to declare a global variable?

Question

WordPress

Good afternoon! Can you please tell me how to declare a global variable in Wordpress? And how to use it?
I need to pass variables from the page template to the function. I try so: in a template global $a; $a=5;
in function global $a; echo $a;
But nothing comes out :( The
task is as follows:
We display records on the main page, but not in the standard way . I already asked, but no one answered.
full filling, so that there are no "holes". As a result, sometimes there are one or two records that are not shown.
At the bottom of the page there is a button "Show more", which Ajax loads the next batch of records.
I need to pass the ID of these records further to the output function, and when the news from the next page that has not yet been shown accumulates, then display the filled line.

Answer 1

Have you tried the standard PHP methods?

Answer 2

*psychic mode*
you have the output of the variable before its definition, if your function is in the functions.php file in the theme. pass it through ajax for example