How to post JSON to PHP with curl

Question

I may be way off base, but I've been trying all afternoon to run the curl post command in this recess PHP framework tutorial. What I don't understand is how is PHP supposed to interpret my POST, it always comes up as an empty array.

curl -i -X POST -d '{"screencast":{"subject":"tools"}}'  \
      http://localhost:3570/index.php/trainingServer/screencast.json

(The slash in there is just to make me not look like an idiot, but I executed this from windows using PHP 5.2, also tried on a Linux server, same version with Linux curl)

There must be something I'm missing because it seems pretty straightforward, the post just isn't be interpreted right, if it was, everything would work great.

This is what I get back:

HTTP/1.1 409 Conflict
Date: Fri, 01 May 2009 22:03:00 GMT
Server: Apache/2.2.8 (Win32) PHP/5.2.6
X-Powered-By: PHP/5.2.6
Transfer-Encoding: chunked
Content-Type: text/html; charset=iso-8859-1

{"screencast":{"id":null,"subject":null,"body":null,
         "dataUrl":null,"dataMedium":null,"createdOn":null,"author":null}}

Answer 1

Jordans analysis of why the $_POST-array isn't populated is correct. However, you can use

$data = file_get_contents("php://input");

to just retrieve the http body and handle it yourself. See PHP input/output streams.

From a protocol perspective this is actually more correct, since you're not really processing http multipart form data anyway. Also, use application/json as content-type when posting your request.

Answer 2

Normally the parameter -d is interpreted as form-encoded. You need the -H parameter:

curl -v -H "Content-Type: application/json" -X POST -d '{"screencast":{"subject":"tools"}}' \
http://localhost:3570/index.php/trainingServer/screencast.json

Answer 3

I believe you are getting an empty array because PHP is expecting the posted data to be in a Querystring format (key=value&key1=value1).

Try changing your curl request to:

curl -i -X POST -d 'json={"screencast":{"subject":"tools"}}'  \
      http://localhost:3570/index.php/trainingServer/screencast.json

and see if that helps any.

Answer 4

You need to set a few extra flags so that curl sends the data as JSON.

command

$ curl -H "Content-Type: application/json" \
       -X POST \
       -d '{"JSON": "HERE"}' \
       http://localhost:3000/api/url

flags

• -H: custom header, next argument is expected to be header
• -X: custom HTTP verb, next argument is expected to be verb
• -d: sends the next argument as data in an HTTP POST request

resources

• cURL manpage
• cURL examples

Answer 5

You should escape the quotes like this:

curl -i -X POST -d '{\"screencast\":{\"subject\":\"tools\"}}'  \
  http://localhost:3570/index.php/trainingServer/screencast.json