Why is my cURL POST JSON data interpreted as empty in PHP?

Posting JSON to PHP Using cURL: An Issue with Data Interpretation

In an attempt to execute a cURL POST command within a recess PHP framework, a user encountered difficulties with interpreting posted data. Specifically, the POST parameter -d was not being recognized as expected, resulting in an empty array.

Problem Statement

A user attempted to utilize the cURL command:

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

Despite executing the command on both Windows (PHP 5.2) and Linux (same PHP version), the POST data was not being interpreted correctly. The server response indicated an empty "screencast" array, as seen below:

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

Solution

The issue stemmed from cURL's default assumption that the -d parameter specifies form-encoded data. To resolve this, the -H parameter must be used to specify the Content-Type as JSON:

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

With this modification, cURL correctly interpreted the posted JSON data and the POST operation succeeded.

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