WP Upload URL to Media Library

upload_url.php

<?php


/**
 * @param $url url to upload
 * @param int $post_id post to attach it to
 *
 * Add a url to the media library and attach it to a post if wanted
 * @return bool|int|string|WP_Error
 */
function upload_url( $url, $post_id = 0 ) {

	require_once( ABSPATH . 'wp-admin/includes/image.php' );
	require_once( ABSPATH . 'wp-admin/includes/file.php' );
	require_once( ABSPATH . 'wp-admin/includes/media.php' );

	$temp_file = download_url( $url );

	if ( is_wp_error( $temp_file ) ) {
		@unlink( $temp_file );
		return $temp_file;
	}

	$file_type = wp_check_filetype( $url );

	if ( ! is_wp_error( $temp_file ) ) {

		// Create Array based on $_FILE with php
		$file = array(
			'name'     => basename( $url ), // ex: wp-header-logo.png
			'type'     => $file_type['type'],
			'tmp_name' => $temp_file,
			'error'    => 0,
			'size'     => filesize( $temp_file ),
		);

		$attachment_id = media_handle_sideload( $file, $post_id );
		@unlink( $temp_file );

		return $attachment_id;
	}

	return false;
}


//Some stuff you can do with the returned ID

//update_post_meta( $attachment_id, '_wp_attachment_image_alt', sanitize_title_with_dashes( get_the_title( $post_id ) ) );
//set_post_thumbnail( $post_id, $attachment_id );