An example of how to create a history event using the REW CRM API

gistfile1.php

<?php

// REW CRM API Key
define('REW_API_KEY', '7220899b054d5ed760f80237a6c0XXXXXXXX30aa2d61235e1efxde52676f1');

// cURL resource
$ch = curl_init();

// Auth headers
$headers = array(
    'X-REW-API-Key: ' . REW_API_KEY,
);

// API Request URL
$request_url = 'http://www.example.com/api/crm/v1/leads/johns@example.com/events';

// POST params
$post_params = array(
	'type' => 'Action',
	'subtype' => 'FormSubmission',
	'details' => array(
		'page' => 'http://www.example.com/contact.html',
		'form' => 'My third-party contact form',
		'data' => array(
			'first_name' => 'John',
			'last_name' => 'Smith',
			'email' => 'johns@example.com',
			'some_other_field' => 'Test Data',
			'comments' => "Hello there!\nThese words are on a new line." . PHP_EOL . 'And so is this!',
		),
	),
);

// Turn POST parameters into a URL-encoded string
$post_params = http_build_query($post_params);

// cURL options
$options = array(
	CURLOPT_URL		=> $request_url,
	CURLOPT_HEADER		=> false,
	CURLOPT_RETURNTRANSFER	=> true,
	CURLOPT_FOLLOWLOCATION	=> false,
	CURLOPT_USERAGENT	=> 'apiClient/1.0',
	CURLOPT_TIMEOUT		=> 60,
	CURLINFO_HEADER_OUT	=> true,
	CURLOPT_CUSTOMREQUEST  	=> 'POST',
	CURLOPT_POSTFIELDS  	=> $post_params,
	CURLOPT_HTTPHEADER	=> $headers,
);

// Set cURL options
curl_setopt_array($ch, $options);

// Execute request & get response
$output = curl_exec($ch);

// Close resource
curl_close($ch);

// Print raw output from API
echo $output . PHP_EOL;

// Print decoded JSON from API
$json = json_decode($output, true);
var_dump($json);

To create a newline, you can either use a \n inside a string wrapped in double-quotes, or concatenate any string with PHP_EOL