将值传递给脚本中的PHP变量

I have some PHP code inside the script so I need the JavaScript value as a PHP variable, as follows:

<script>
;
 var js_var = 123;
 var php_var = <?php js_var ?>;
 alert(php_var);
;
</script>

Using jQuery to send the value to a PHP page will return the value but not as a PHP variable:

$.get("page.php", {js_var_name: js_var}, function(data) {alert(data)});

I tried also all jQuery AJAX functions: load(), post() and the ajax() method, none of them pass back the value of PHP as above requested.

Is it possible to implement the above with jQuery?

Likely you have a syntax issue with :

var php_var = <?php js_var ?>;

Unless you used define() your php variable should start with $ and you need to echo it so that it gets printed to the page

var php_var = <?php echo $js_var ?>;

If you are assuming that php will read the prior javascript js_var=123 it won't. Javscript is a client side language and php is server side.

You cannot simply mix PHP and JavaScript. The former is executed on the server, the latter on the client, namely in the user's browser. In order to hand a value from PHP to JavaScript you need to output JavaScript code via PHP or do a AJAX-Request to a PHP-Script, as you tried. When using AJAX, it is the easiest solutions to have PHP script that returns a JSON string. When calling this script using $.get() the result will be stored in a JavaScript variable and you can access all the values from there.

Take a moment and a deep breath...and then start thinking about your scopes again.