How to Upload an Image to Media Manager via WordPress REST API

Hello. In today’s article, we’ll look at uploading images to the WordPress media manager using the API and its core functions.
Today we’ll add some complexity by using a cron job. Our code will need to execute every 10 seconds.
Let’s get started. First, we’ll create a custom time interval for the cron job using the WordPress “cron_schedules” filter:

add_filter('cron_schedules', function ($schedules)
{
	$schedules['10sec'] = [
		'interval' => 10,
		'display'  => __('Every 10 sec'),
	];
	return $schedules;
});

In our case, we’re adding another array to the “$schedules” variable. The key is our custom interval. Inside the array:
“interval” — duration in seconds, “display” — label for the interval.

In the following snippet:

add_action('wp', function(){
	if(!wp_next_scheduled('rest_api_media'))
	{
		wp_schedule_event( time(), '10sec', 'rest_api_media');
	}
});

We trigger the hook that we’ll define later, set to fire every 10 seconds.
The WordPress function “wp_next_scheduled('rest_api_media')” checks whether the specified hook should run at this moment.
If it should — we schedule it with “wp_schedule_event” and set the timestamp.

Now the main code responsible for uploading an image to our or another WordPress site via API:

add_action('rest_api_media', function ()
{
	$username = 'admin';
	$password = 'qweqwe';
	$headers = [
		'Authorization' => 'Basic ' . base64_encode($username . ':' . $password),
	];

	
	$url = мой-сайт/wp-json/wp/v2/media/';
	$file = __DIR__ . '/data/book.jpg';
	$headers['Content-Disposition'] = 'attachment; filename="' . basename($file) . '"';
	$response = wp_remote_post($url, [
		'headers' => $headers,
		'body' => file_get_contents($file)
	]);


	$records = json_decode(
		wp_remote_retrieve_body($response), 
		true
	);

	echo '<strong>Code:</strong> ' . wp_remote_retrieve_response_code($response);
	echo '<br>';
	echo '<strong>Message:</strong> ' . wp_remote_retrieve_response_message($response);
	echo '<br>';
	echo '<strong>Records:</strong> ' . count($records);
	echo '<br>';
	echo '<strong>Answer:</strong>';
	echo"<pre>\$records = ";print_r($records);echo"</pre>";
	// die;
});

Uploading images through the API was the hardest part for me when working with REST.
There’s almost no information online, and the little I found didn’t help.

Let’s break down the code above. First, we prepare the request headers for authentication.
This is essential — without it, we won’t be able to upload anything.

Here:

$url = мой-сайт/wp-json/wp/v2/media/';
$file = __DIR__ . '/data/book.jpg';
$headers['Content-Disposition'] = 'attachment; filename="' . basename($file) . '"';
$response = wp_remote_post($url, [
	'headers' => $headers,
	'body' => file_get_contents($file)
]);

We specify the site URL where the file will be uploaded.

The “$file” variable contains the full path to the file.

And this is the header that declares the name of the uploaded file:

$headers['Content-Disposition'] = 'attachment; filename="' . basename($file) . '"';

Then, using “wp_remote_post”, we send the file contents through the “body” parameter after reading them:

$response = wp_remote_post($url, [
	'headers' => $headers,
	'body' => file_get_contents($file)
]);

The site’s API will return a detailed response about the uploaded file.
We can debug and inspect it using this code:

$records = json_decode(
	wp_remote_retrieve_body($response), 
	true
);

echo '<strong>Code:</strong> ' . wp_remote_retrieve_response_code($response);
echo '<br>';
echo '<strong>Message:</strong> ' . wp_remote_retrieve_response_message($response);
echo '<br>';
echo '<strong>Records:</strong> ' . count($records);
echo '<br>';
echo '<strong>Answer:</strong>';
echo"<pre>\$records = ";print_r($records);echo"</pre>";

That’s it — image upload complete.