具有ServerSide的数据表发送表单数据，但$ _POST为空

Question

我已经使用ServerSide配置了一个DataTable。

$("#tablaProductos").DataTable({
    "Processing": true,
    "serverSide": true,
    "ajax": {
        "url": "ajax/datatable-productos.ajax.php",
        "type": "POST"
    } });

网络通讯显示：一般

Request URL: http://localhost/POS_TH/ajax/datatable-productos.ajax.php
Request Method: POST
Status Code: 200 OK
Remote Address: [::1]:80
Referrer Policy: no-referrer-when-downgrade

响应标题

Cache-Control: no-store, no-cache, must-revalidate
Connection: Keep-Alive
Content-Encoding: gzip
Content-Length: 294
Content-Type: text/html; charset=UTF-8
Date: Fri, 22 Nov 2019 15:31:15 GMT
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Keep-Alive: timeout=5, max=83
Pragma: no-cache
Server: Apache/2.4.34 (Ubuntu)
Vary: Accept-Encoding

请求标题

Accept: application/json, text/javascript, /; q=0.01
Accept-Encoding: gzip, deflate, br
Accept-Language: es-ES,es;q=0.9,en;q=0.8,ca;q=0.7
Connection: keep-alive
Content-Length: 1569
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Cookie: P...
Host: localhost
Origin: http://localhost
Referer: http://localhost/POS_TH/productos
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-origin
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.120 Safari/537.36
X-Requested-With: XMLHttpRequest

表格数据

draw: 1
columns[0][data]: 0
columns[0][name]:
columns[0][searchable]: true
columns[0][orderable]: true
columns[0][search][value]:
columns[0][search][regex]: false
columns[1][data]: 1
columns[1][name]:
columns[1][searchable]: true
...
search[regex]: false

datatable-productos.ajax.php中的var_dump($_POST);是： var_dump($_POST); 响应为： array(0) { }

我已经在数据表配置和var_dump(file_get_contents("php://input"))尝试了"contentType": "application/json" ，但没有任何变化。

如果我通过GET更改了ajax类型并读取了$ _GET，我将发送所有参数（绘制，...），为什么？ 如何使用POST类型？