如何使用ajax和PHP将数据传递到服务器？ $ _POST ['data']不起作用

Question

I have an HTML form that I want to send to the server (using a PHP script) some information before it gets submitted. I'm using .ajax() jQuery function as well.

Here's my demo.html file:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div class="form-group">
<label>Provincia</label>
<select id ="demo" class="form-control">
<option> </option>
<option value="op1">Opcion 1</option>
<option value="op2">Opcion 2</option> 
<option value="op3">Opcion 3</option> 
</select>
</div>

<div id="demo2"></div>

<script>

$(document).ready(function() {
    $('#demo').on('change', do_something);
    console.log('ready');
});

function do_something() {
    var selected = $('#demo').val();
    $.ajax({
        url:        'delete.php',
        type:       'POST',
        dataType:   'json',
        data:       { selected }
    });
    console.log(selected);
    $('#demo2').append(selected);
}
</script>

I don't know what to do to get the selected item. I get to print the selected item on the screen and in the console. How do I get that with PHP?

The delete.php file has only this:

<?php
var_dump($_POST['data']);
var_dump($_POST['selected']);

Because I want to know what's on the server, but nothing gets printed. How may I get what's been selected?

Answer 1

Use data attribute to set values you want to send to PHP and you can also set success to execute code when the request is successful.

function do_something() {
    var selected = $('#demo').val();
    $.ajax({
        url:        'delete.php',
        type:       'POST',
        dataType:   'json',
        data:       { selected: selected },
        success: function (response) {
            // response comes from PHP
            if (response.result == true) {
                // request was success
            }else if (response.result == false) {
                // request was not successful
            }
        }
    });
}

Then in your PHP, you can access the values through $_POST

<?php

$selected = $_POST['selected'];

// rest of the code here
// you can also send response to Javascript here
// for failure echo json_encode(['result' => false]);
// for success echo json_encode(['result' => true])