为什么$ _POST从ajax请求中得不到任何东西？

Question

var httpRequest = new XMLHttpRequest();
httpRequest.onreadystatechange = action;
httpRequest.open('POST','/fetch_product_list.php','true');
httpRequest.send("var=5");

但在fetch_product_list.php中，$ _POST ['var']什么都没有，我该如何解决？

Answer 1

您尚未为请求正文添加内容类型。

httpRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

Answer 2

添加行：httpRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");，因此代码如下：

var httpRequest = new XMLHttpRequest();
httpRequest.onreadystatechange = action;
httpRequest.open('POST','/fetch_product_list.php','true');
httpRequest.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
httpRequest.send("var=5");

并在php中使用：$_POST['var']。