javascript - Error by passing variable from JS to PHP -

i know question answered 1 million times i'm becoming desperate code.

i have 2 files php files , want send variable part written in js other php file. here's code:

carga_datos.php

<script>     function myalert() {             var radio1 = $("input[name='inputtipoactividad']:checked").val();             $.ajax({                 url : 'post.php',                 type : "post",                 data: {'radio1' : radio1},                 datatype:'json',                 success : function(data) {                      alert(data);                 },             });         }    </script> 

i'm calling myalert() in radio button form

post.php

<?php      $radio1 = $_post['radio1'];     echo $radio1; ?> 

and call post.php carga_datos.php this:

and error i'm retrieving:

notice: > undefined index: radio1 in c:\xampp\htdocs\gis\post.php on line 2

edit:

it seems have used datatype "json" expect "json", if none returned undefined or empty response.

if remove datatype: "json" should able retrieve data fine.

    function myalert() {     var radio1 = $("input[name='inputtipoactividad']:checked").val();     $.ajax({         url : 'post.php',         method : "post",         data: {"radio1" : radio1},         success : function(data) {             console.log(data);         }     }); } 

if want check "datatype: 'json'" still in code, need return php code following:

<?php echo json_encode($_post); ?> 

this either return $_post data or empty [] array.

// old answer true/false values

if want see if checkbox checked or not retrieve boolean, please try following:

var radio1 = $("input[name='inputtipoactividad']").prop("checked"); 

this return true or false. if not wrong, if use

$("input[name='inputtipoactividad']:checked").val() 

it'll return "on" or nothing (might wrong here though).

tested ".prop("checked")" , worked me.