How to set featured image programmatically from url?

// Add Featured Image to Post
$image_url        = 'http://s.wordpress.org/style/images/wp-header-logo.png'; // Define the image URL here
$image_name       = 'wp-header-logo.png';
$upload_dir       = wp_upload_dir(); // Set upload folder
$image_data       = file_get_contents($image_url); // Get image data
$unique_file_name = wp_unique_filename( $upload_dir['path'], $image_name ); // Generate unique name
$filename         = basename( $unique_file_name ); // Create image file name
 // Check folder permission and define file location
if( wp_mkdir_p( $upload_dir['path'] ) ) {
  $file = $upload_dir['path'] . '/' . $filename;
} else {
  $file = $upload_dir['basedir'] . '/' . $filename;
}
 // Create the image  file on the server
file_put_contents( $file, $image_data );
 // Check image file type
$wp_filetype = wp_check_filetype( $filename, null );
 // Set attachment data
$attachment = array(
    'post_mime_type' => $wp_filetype['type'],
    'post_title'     => sanitize_file_name( $filename ),
    'post_content'   => '',
    'post_status'    => 'inherit'
);
 // Create the attachment
$attach_id = wp_insert_attachment( $attachment, $file, $post_id );
 // Include image.php
require_once(ABSPATH . 'wp-admin/includes/image.php');
 // Define attachment metadata
$attach_data = wp_generate_attachment_metadata( $attach_id, $file );
 // Assign metadata to attachment
wp_update_attachment_metadata( $attach_id, $attach_data );
 // And finally assign featured image to post
set_post_thumbnail( $post_id, $attach_id );