API.php

<?php

function callAPI($method, $url, $data, $headers = false){
   $curl = curl_init();

   switch ($method){
      case "POST":
         curl_setopt($curl, CURLOPT_POST, 1);
         if ($data)
            curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
         break;
      case "PUT":
         curl_setopt($curl, CURLOPT_CUSTOMREQUEST, "PUT");
         if ($data)
            curl_setopt($curl, CURLOPT_POSTFIELDS, $data);			 					
         break;
      default:
         if ($data)
            $url = sprintf("%s?%s", $url, http_build_query($data));
   }

   // OPTIONS:
   curl_setopt($curl, CURLOPT_URL, $url);
   curl_setopt($curl, CURLOPT_HTTPHEADER, array(
      'APIKEY: 111111111111111111111',
      'Content-Type: application/json',
   ));
   curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
   curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);

   // EXECUTE:
   $result = curl_exec($curl);
   if(!$result){die("Connection Failure");}
   curl_close($curl);
   return $result;
}

requests.php

<?php
// GET
$get_data = callAPI('GET', 'https://api.example.com/get_url/'.$user['User']['customer_id'], false);
$response = json_decode($get_data, true);
$errors = $response['response']['errors'];
$data = $response['response']['data'][0];


// POST
$data_array =  array(
      "customer"        => $user['User']['customer_id'],
      "payment"         => array(
            "number"         => $this->request->data['account'],
            "routing"        => $this->request->data['routing'],
            "method"         => $this->request->data['method']
      ),
);

$make_call = callAPI('POST', 'https://api.example.com/post_url/', json_encode($data_array));
$response = json_decode($make_call, true);
$errors   = $response['response']['errors'];
$data     = $response['response']['data'][0];

// PUT
$data_array =  array(
   "amount" => (string)($lease['amount'] / $tenant_count)
);

$update_plan = callAPI('PUT', 'https://api.example.com/put_url/'.$lease['plan_id'], json_encode($data_array));
$response = json_decode($update_plan, true);
$errors = $response['response']['errors'];
$data = $response['response']['data'][0];

// DELETE
callAPI('DELETE', 'https://api.example.com/delete_url/' . $id, false);