为什么我的$ _POST为空，但file_get_contents（'php：// input'）不是？

Question

When I POST data to my server using a regular old form submit I can pull that data from the $_POST variable, but when POST ing JSON data via AJAX I need to access it via file_get_contents('php://input') . Why is that? In both cases I am using the POST method, are there some explicit headers I should be setting on my AJAX call? I have only ever come up against this problem on the current development server and have never had to use file_get_contents('php://input') before. Is there a server setting somewhere? Can I change this behaviour with a .htaccess?

Answer 1

Add this to the top of your .php file:

$_POST = json_decode(file_get_contents("php://input"), true);

so that the contents will be property decoded and available. After that, you can access individual keys as usual.

Answer 2

So as far as I have been able to find out, this has something to do with the way the data is received by the server - PHP can't natively parse JSON. Sending plain old JSON objects from Javascript to PHP will result in PHP not knowing what to do with the datatype, and thus it won't be able to prepopulate the appropriate global variables.

In order to get around it I added a check to my ajax wrapper function that intercepts the JSON, encodes is as a FormData object and shoots that off to the server instead.