Deletion of a course_enrollment record via web services removes all related learner content, including the course_report record, course_outline_fulfillment records, and course_credit_awarded records. It will also cascade deletions to the child enrollments if deleting the parent course of a course relationship.
$curl = curl_init("http://your-domain.com/course_enrollment/1234"); // Note the 1234, which is the enrollment id of the course_enrollment entity record
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, 'DELETE');
curl_setopt($curl, CURLOPT_HTTPHEADER, array("Content-Type: application/json"));
curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
curl_setopt($curl, CURLOPT_USERPWD, "restws_webservice:webservice_password"); //Your credentials goes here
curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);
print 'Deleting...';
$json = curl_exec($curl);
$cinfo = curl_getinfo($curl);
$response = json_decode($json);
if($cinfo['http_code'] == 200 && empty($response)){
print 'The entity has been deleted'.
}