How to pass javascript variable value to php?

Question

How can I move to a variable php the value of a select, whenever a different option is selected.

I tried as below, but returns me [Object Htmlselectelement]

$("select#tipo_documento").change(function (event) {

            var tipo_documento = document.getElementById('tipo_documento').value;
})

<?php
                $tipo_documento = "<script>"

         . "document.write(tipo_documento)"

         . "</script>";
            ?>

Answer 1

You are mixing FRONTEND (Javascript) codes with BACKEND (PHP) codes).

It is possible to pass the value of the Javascript variable tipo_documento via Ajax to an archive PHP.

$("select#tipo_documento").change(function (event) {
      var tipo_documento = document.getElementById('tipo_documento').value;
      var req = this.createXMLHTTPObject();
      if (!req) return;
      var url = 'http://www.seu_site.com.br/seu_php.php?tipo_documento = ' . tipo_documento;
      req.open('GET',url,true);
      req.onreadystatechange = function () {          
        if (req.readyState != 4) {
            return;
        }
        if (req.status != 200 && req.status != 304) {
            alert('HTTP error ' + req.status);
            return;
        }


        alert('ok');
    }
    if (req.readyState == 4) return;
    req.send();


});

Answer 2

I have been through this doubt and after a long time thinking I found an extremely simple solution of pass a js or HTML variable to PHP.

I basically created a form that when the input (type="Submit") would send an html/js variable to php ... that can be used on the page itself or even on another page. another method can also be used... you can set a cookie in php of name your choice to be sent ... in case you would use the code:

setcookie('nome do cookie', '<script>document.write(varivel);</script>' , time()+(30*24*3600));

Answer 3

Use an Hide text element with a unique id. Or open and close the PHP tag with echo in value. But you have to take into account the HTML creation order in the browser.