<?php
$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => "https://app.userengage.com/api/public/users/",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "{'email': 'myemail@mydomain.com','first_name': 'John',  'last_name': 'Doe'}",
  CURLOPT_HTTPHEADER => array(
    "authorization: Token <bug53ggTj9NQHtlQiyrzLf2LXadurwIb5TfFMEXU6FC9E9KH2m45AQcCEW4fBIqr>",
    "content-type: application/json"
  ),
));

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}