WordPress External Image Handler - Add External URL image as featured image for a post

wp-external-image-handler.php

/**
 * Uploads an image from remote url and sets as featured image of the new post
 *
 * @param int    $post_id       The id of the new post
 * @param string $thumbnail_url Url of the preview image hosted by BrightTalk
 */
private function image_handler( $post_id, $thumbnail_url ) {
    
    $image_url        = $thumbnail_url; // Define the image URL here
    $image_name       = basename( $thumbnail_url );
    $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 );
}