[PHP][WORDPRESS] Upload files from external url to media gallery

functions.php

<?php

function uploadToAttachmentsFromURL($url)
{

	$upload_dir = wp_upload_dir();

	$image_data = file_get_contents($url);

	$filename = basename($url);

	if (wp_mkdir_p($upload_dir['path'])) {
		$file = $upload_dir['path'] . '/' . $filename;
	} else {
		$file = $upload_dir['basedir'] . '/' . $filename;
	}

	file_put_contents($file, $image_data);

	$wp_filetype = wp_check_filetype($filename, null);

	$attachment = array(
		'post_mime_type' => $wp_filetype['type'],
		'post_title' => sanitize_file_name($filename),
		'post_content' => '',
		'post_status' => 'inherit'
	);

	$attach_id = wp_insert_attachment($attachment, $file);
	require_once(ABSPATH . 'wp-admin/includes/image.php');
	$attach_data = wp_generate_attachment_metadata($attach_id, $file);
	wp_update_attachment_metadata($attach_id, $attach_data);

	return $attach_id;
}