Create featured image from a remote url when creating a post

Question

I am trying to scrape an image from a remote url that is added using a text field in Advanced Custom Fields (hardcoded in the example below), but I don't even know if the process I am using is correct. I read multiple sources, but different functions and techniques are used (media_sideload_image, wp_remote_get, etc), so I am a bit confused.

I used multiple sources to create the following code.

The scraper from here (tested on its own for the following example, works just fine): https://www.ostraining.com/blog/coding/extract-image-php/

I used some info on this post: https://stackoverflow.com/questions/31368072/error-in-fetching-image-using-wp-remote-get-function

And the docs: https://codex.wordpress.org/Function_Reference/media_handle_sideload

So here is my code:

function generate_featured() {
    global $post;
    if($update == false) {
        if ( !function_exists('media_handle_upload') ) {
            require_once(ABSPATH . "wp-admin" . '/includes/image.php');
            require_once(ABSPATH . "wp-admin" . '/includes/file.php');
            require_once(ABSPATH . "wp-admin" . '/includes/media.php');
        }

        $url = 'https://www.google.gr';
        $html = file_get_contents($url);
    preg_match_all( '|<img.*?src=[\'"](.*?)[\'"].*?>|i',$html, $matches );
    $image_url = $url . $matches[1][0];

        $tmp = download_url( $image_url );
        $file_array = array(
        'name'     => $post_id . '_' . $image_url . '_' . basename( $matches[1][0] ),
        'tmp_name' => $tmp
        );

        // Check for download errors
        if ( is_wp_error( $tmp ) ) {
            @unlink( $file_array['tmp_name'] );
            return false;
        }

        $id = media_handle_sideload( $file_array, $post_id );

        // Check for handle sideload errors.
        if ( is_wp_error( $id ) ) {
            @unlink( $file_array['tmp_name'] );
            return false;
        }

        // Set post thumbnail.
        set_post_thumbnail( $post_id, $id );
    }
}
add_action( 'save_post', 'generate_featured', 10, 3 );

The thing is I don't see any files created on the wp-content/uploads directory. I temporarily used the media_sideload_image($file, $post_id, $desc); function and the file gets created properly but cannot then set it as a featured image.

Any help is appreciated!

Answer 1

The code worked for me; but I defined the function like this: function generate_featured( $post_id ), then I commented out the global $post;; and finally (although this is not mandatory..), in the $file_array, I set name like this: 'name' => basename( $image_url ),

So: (Note that I intentionally didn't include the whole code)

function generate_featured( $post_id, $post, $update ) {
    //global $post;
    if($update == false) {
        ...

        $tmp = download_url( $image_url );
        $file_array = array(
        'name'     => basename( $image_url ),
        'tmp_name' => $tmp
        );

        ...

        // Set post thumbnail.
        set_post_thumbnail( $post_id, $id );
    }
}
add_action( 'save_post', 'generate_featured', 10, 3 );

See https://developer.wordpress.org/reference/hooks/save_post/ if you need (further) help with the save_post hook.