YOU CAN'T pass a jQuery variable to the PHP code "on this page".
Because the "PHP code on this page" ran in the past. It created a page, sent it to the browser, and exited.
What is it that you are really trying to accomplish?
This sounds more like a PHP question, which you should ask in a PHP forum. You can certainly pass a variable to SOME PHP code (not necessarily a "page"). To do SOMETHING (what?).
$.ajax('/some/url/on/your/site', {
type: 'POST', // or 'GET' or whatever
data: { choice: choice}
}).done(function(response) {
// maybe do something with the result here
});
If you just want your PHP to create a new page, you don't need Ajax.