PHP - Crear cURL PHP

curl -k -X POST -H "X-API-Key: ca9e513e" -H "Content-Type: application/json" -H "Accept: application/json" "https://domain.com/api/v2/" -d '{ "params": ["--create", "user@mail.com", "-passwd", "pwres123", "-mailbox", "true"]}'

$ch = curl_init($url);

curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "GET");

$ch = curl_init($url);

curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($usuario));

curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type:application/json'));

curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");