Upload image in Wordpress media using Wordpress API REST using wp_remote_post.

wordpress-remote-image-upload.php

<?php
//Add this to your function.php
function upload_image( $imageID, $login ) {
  $request_url = 'https://DOMAINNAME.com/wp-json/wp/v2/media'; //change the domainname
	$image_file_path = get_attached_file($imageID); //change this to your file meda path if your not throwing media file to other server
  $image = file_get_contents( $image_file_path );
	$mime = mime_content_type( $image_file_path );
	
  $api_media_response = wp_remote_post( $request_url, array(
		'headers' => array(
			'Authorization' => 'Basic ' . base64_encode( $login ), //login format USERNAME:PASSWORD
			'Content-Disposition' => 'attachment; filename='.basename($image_file_path).'',
			'Content-Type' => $mime
		),
		'body' => $image
	) );
  
  //this function return wp_remote_post
  // more info => https://developer.wordpress.org/reference/functions/wp_remote_post/
}