Using FormData object, the server receives an empty POST

问题

I'm attempting to send one file and one text variable to my server with the FormData object. Looking at the Network tab in Chrome's developer tools, I can see that the file and variable are being sent. However, I've tried var_dump() on the $_POST and $_FILES variables, and both are shown as empty arrays. Here's the code I'm using for the form:

var image_upload = document.getElementById("image_upload");

if(image_upload.value == '')
{
   alert("Please select a file to upload.");
}
else
{
   alert("in");
   var ajaxHandler = new XMLHttpRequest();
   var content = image_upload.files[0];
   var formData = new FormData();
   formData.append("type", "5");
   formData.append("content", content)

   ajaxHandler.onreadystatechange = function() {
      if(ajaxHandler.readyState == 4)
      {
         alert(ajaxHandler.responseText);
      }
   };

   ajaxHandler.open("POST", "newCard", false);
   ajaxHandler.setRequestHeader("Content-type","multipart/form-data");
   ajaxHandler.send(formData);
}

I have tried this code with and without "charset=utf-8" in the content type, and it doesn't seem to make a difference. What's going on here?

回答1:

Remove the ajaxHandler.setRequestHeader("Content-type","multipart/form-data"); from the code. The proper multipart/form-data header should contain boundary string. Browser automatically set that header, if you add file in FormData.

来源：https://stackoverflow.com/questions/10326955/using-formdata-object-the-server-receives-an-empty-post