About how PHP gets AJAX values.

The question about how PHP can obtain AJAX values .......... Now you have the following question 1. the php page has a & lt; select & gt;, as shown below & lt; div & gt; test: & nbsp; & nbsp; & lt; select & nbsp; id = "top questions about how PHP gets AJAX values ..........
The following problems exist:
1. there is , The following test: 10 20 30


Then there is a variable $ arr on this page.

Now I want to assign the option value to $ arr, and change the value of $ arr every time the option is changed.
Then I used AJAX to return the json value. each time the option is changed, the values are 10, 20, 30, respectively.
My question is how to pass the AJAX value to $ arr.
------ Solution --------------------
To modify a value on the main interface of ajax, you can use js to change the value on the page.
Ajax is executed by js. you can simply add a statement to the callback function.
Add a div or span to set an id, and then write a js statement.
If you want to change a lot of values, simply replace the content of the entire page.