Using several custom fields as custom post title

Question

I have stumbled upon a brilliant piece of code that just fits my needs on this thread : Using custom field as custom post title by @chrisguitarguy and I was hoping there might be a way to tweak it to use several custom fields' input to populate a CPT's title.

For example, to be sure there will never be any case of twice the same title being generated I would like to use a custom field named dlc_media_photos_titre followed by another named dlc_media_photos_date, this way I should obtain a title in this format : Photo gallery name 20210921.

The date format doesn't really matter, it is just a security to include it in the title.

Thanks in advance (and excuse me if my post is not usual, it is my first one on StackExchange/Overflow).

edit Yes I will add the code i am using next time, it's so obvious ! Thanks a lot for your help

edit 30/06/2022 I have an addition to bring : @Michelle's code works perfectly, but in case you want to combine the value of a Taxonomy with custom fields, this code will work :

add_filter( 'the_title', 'custom_post_title', 10, 2 );
function custom_post_title( $title, $post_id ) {
    $post_type = get_post_type( $post_id );
    if ( $post_type == 'my-post-type' ) {
        $taxonomy = get_the_terms( $post_id, 'my-taxonomy-name' );
        $taxonomy = $taxonomy[0]->name;
        $custom_field = get_post_meta( $post_id, 'my-custom-field', true );
        $title = $taxonomy . ' - ' . $custom_field;
    }
    return $title;
}

Answer 1

Ideally you should include the code you've already tried with your question so we can help with that, just a tip. :) But if you're using the code from that other post as-is, the change would be to this bit:

add_filter( 'the_title', 'wpse33385_filter_title', 10, 2 );
function wpse33385_filter_title( $title, $post_id )
{
    if( $new_title = get_post_meta( $post_id, 'custom_field_name', true ) )
    {
        return $new_title;
    }
    return $title;
}

Where the original only references one custom field, you need to grab two and then use both:

add_filter( 'the_title', 'wpse33385_filter_title', 10, 2 );
function wpse33385_filter_title( $title, $post_id )
{
    $photos_title = get_post_meta( $post_id, 'dlc_media_photos_titre', true );
    $photos_date = get_post_meta( $post_id, 'dlc_media_photos_date', true );

    if( $photos_title && $photos_date) {
        $new_title = $photos_title . ' ' . $photos_date;
        return $new_title;
    }
    return $title;
}

Note that the line $new_title = $photos_title . ' ' . $photos_date; is adding a space between the output of the two fields. If you wanted something else there, a | (pipe symbol) for instance, you could do:

$new_title = $photos_title . ' | ' . $photos_date;