How to get body of a POST in php?

I submit as POST to a php page the following:

{a:1}

This is the body of the request (a POST request).
In php, what do I have to do to extract that value?

var_dump($_POST); 

is not the solution, not working.

To access the entity body of a POST or PUT request (or any other HTTP method):

$entityBody = file_get_contents('php://input');

Also, the STDIN constant is an already-open stream to php://input, so you can alternatively do:

$entityBody = stream_get_contents(STDIN);

From the PHP manual entry on I/O streams^docs:

php://input is a read-only stream that allows you to read raw data from the request body. In the case of POST requests, it is preferable to use php://input instead of $HTTP_RAW_POST_DATA as it does not depend on special php.ini directives. Moreover, for those cases where $HTTP_RAW_POST_DATA is not populated by default, it is a potentially less memory intensive alternative to activating always_populate_raw_post_data. php://input is not available with enctype="multipart/form-data".

Specifically you'll want to note that the php://input stream, regardless of how you access it in a web SAPI, is not seekable. This means that it can only be read once. If you're working in an environment where large HTTP entity bodies are routinely uploaded you may wish to maintain the input in its stream form (rather than buffering it like the first example above).

To maintain the stream resource something like this can be helpful:

<?php

function detectRequestBody() {
    $rawInput = fopen('php://input', 'r');
    $tempStream = fopen('php://temp', 'r+');
    stream_copy_to_stream($rawInput, $tempStream);
    rewind($tempStream);

    return $tempStream;
}

php://temp allows you to manage memory consumption because it will transparently switch to filesystem storage after a certain amount of data is stored (2M by default). This size can be manipulated in the php.ini file or by appending /maxmemory:NN, where NN is the maximum amount of data to keep in memory before using a temporary file, in bytes.

Of course, unless you have a really good reason for seeking on the input stream, you shouldn't need this functionality in a web application. Reading the HTTP request entity body once is usually enough -- don't keep clients waiting all day while your app figures out what to do.

Note that php://input is not available for requests specifying a Content-Type: multipart/form-data header (enctype="multipart/form-data" in HTML forms). This results from PHP already having parsed the form data into the $_POST superglobal.

return value in array

 $data = json_decode(file_get_contents('php://input'), true);

A possible reason for an empty $_POST is that the request is not POST, or not POST anymore... It may have started out as post, but encountered a 301 or 302 redirect somewhere, which is switched to GET!

Inspect $_SERVER['REQUEST_METHOD'] to check if this is the case.

See https://stackoverflow.com/a/19422232/109787 for a good discussion of why this should not happen but still does.