PHP Curl POSTing JSON example

<?php
$base_url = "https://openapi.octoparse.com";
$token_url = $base_url . '/token';

$post =[
    'username' => 'igorsavinkin',
	'password' => '<xxxxxx>', 
	'grant_type' => 'password' 
];

$payload = json_encode($post);

$headers = [
	'Content-Type: application/json' ,
	'Content-Length: ' . strlen($payload)
];

$timeout = 30;
$ch_upload = curl_init(); 
curl_setopt($ch_upload, CURLOPT_URL, $token_url);
if ($headers) { 
	curl_setopt($ch_upload, CURLOPT_HTTPHEADER, $headers);
} 
curl_setopt($ch_upload, CURLOPT_POST, true); 
curl_setopt($ch_upload, CURLOPT_POSTFIELDS, $payload /*http_build_query($post)*/ );
curl_setopt($ch_upload, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch_upload, CURLOPT_CONNECTTIMEOUT, $timeout);
$response = curl_exec($ch_upload);

if (curl_errno($ch_upload)) {
    echo 'Curl Error: ' . curl_error($ch);
}

curl_close($ch_upload); 
//echo 'Response length: ', strlen($response);
echo  $response ;
$fp = fopen('octoparse-api-token.json', 'w') ;
fwrite($fp, $response );
fclose($fp);