How to equate a php variable with a javascript var

Hi
I have some js code in my .php file
In the js code I have a variable "names"
I need to tell php the value of this variable and call it $names
How can I do that?
Thank you for your help

 

Have you ever heard of AJAX ?

 

Does the PHP script only need to know the value of this variable once the page is submitted? Because if that's the case, you can stick the updates value of names into a hidden input field, and use an onPageUnload() function to send the value to the php script through a post submission.