How to post raw data using CURL in PHP?

Question: How to POST data using CURL in PHP?

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,            "http://domain.com/ajax/postdata" );
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 );
curl_setopt($ch, CURLOPT_POST,           1 );
curl_setopt($ch, CURLOPT_POSTFIELDS,     '{"2016-3-18":[],"2016-03-19":[["15:00","19:00"]],"2016-3-18":[],"2016-3-19":[],"2016-3-20":[],"2016-3-21":[],"2016-3-22":[],"2016-3-23":[],"2016-3-24":[],"2016-3-25":[],"2016-3-26":[],"2016-3-27":[],"2016-3-28":[],"2016-3-29":[],"2016-3-30":[],"2016-3-31":[],"2016-4-1":[],"2016-4-2":[],"2016-4-3":[],"2016-4-4":[],"2016-4-5":[],"2016-4-6":[],"2016-4-7":[],"2016-4-8":[],"2016-4-9":[],"2016-4-10":[],"2016-4-11":[],"2016-4-12":[]}' ); 
curl_setopt($ch, CURLOPT_HTTPHEADER,     array('Content-Type: text/plain')); 
echo $result=curl_exec ($ch);

Question: How to read Raw data with PHP?

     $rawData= file_get_contents('php://input');
     /** Use the rawData **/

     /** Use the rawData **/

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