Displaying a dropdown menu of custom post titles with ACF (Advanced Custom Fields) in WordPress

I would like to display a list of custom post titles with the help of Advanced Custom Fields.

First off, I have created a custom post type.

function create_posttype() {
     register_post_type(
         'room',
         array(
             'labels' => array(
                 'name' => __('Conference rooms'),
                 'singular_name' => __('Conference room')
             ),
             'menu_icon' => 'dashicons-building',
             'menu_position' => 5,
             'public' => true,
             'has_archive' => false,
             'publicly_queryable' => false,
             'show_ui' => true,
             'show_in_menu' => true,
             'query_var' => true,
             'rewrite' => false,
             'capability_type' => 'post',
             'supports' => array('title')
         )
     );
}

Then I have created a few “posts” inside this custom post type ie. Room 01, Room 02, etc. Next, I have created a new Custom Field for each room and set the Location Rule to point to the appropriate room, using ACF.

The fields for each room include:

1. Field Label: Room name,

   Field Name: room_name,

   Field Type: Text,

   Default Value: Room 01 (each room has a different value ie. Room 02, Room 03,…)

2. Field Label: Price per night,

   Field Name: price_per_night,

   Field Type: Number,

   Default Value: 5

3. Field Label: Post object,

   Field Name: post_object,

   Field Type: Post Object,

   Return Format: Post Object

After this, I returned to the custom post type (room) and edited every room (Room 01, etc), so the Post object points to the appropriate page (in this case a page named Reservation with its custom template).

That being done, I opened up the custom template PHP file (which Reservation is using) and added this code, which I copied from the ACF documentation.

<?php
$featured_post = get_field('featured_post');
if( $featured_post ): ?>
    <h3><?php echo esc_html( $featured_post->post_title ); ?></h3>
<?php endif; ?>

Not knowing what I have to call in the get_field section I searched for a room in my WP, which pointed me to ?room=room-01. Looking up get_field() I assume I have to point to the field in which I want to be displayed (argument 1) and the location where the field is located (argument 2).

Now, no matter what I try, I can’t get the title drop-down menu to appear…

A few things I have tried:

$featured_post = get_field('room', 'room=room-01');
$featured_post = get_field('room_name', 'room=room-01');
$featured_post = get_field('room_name', 'room');

If I omit the if statement I get this warning/notice:

Notice: Trying to get property ‘post_title’ of non-object

To conclude, I can’t seem to get it to work. Any help, pointers, advice, and explanations would be most welcome.

If I can provide any additional information, feel free to ask.

Answer

After a lot of searching I have found some related questions and after some work I came up with this…

It’s not what I wanted exactly but it works…

                    <form>
                        <label for ="room">Select a room:</label>
                        <select name="room" id="room">
                    <?php
                    $args = array(
                        'post_type' => 'room',
                        'posts_per_page' => -1,
                        'orderby' => 'title',
                        'order' => 'ASC'
                    );
                    $the_query = new WP_Query($args);
                    $sobe = get_posts($args);
                    foreach ($sobe as $post){
                        setup_postdata($post);
                        $room_title = get_field('room_name');
                        
                        ?>
                        <option value=" <?php echo $room_title ?> " > <?php echo $room_title ?> </option>
                        
                        <?php
                        
                        
                    }
                    wp_reset_postdata();
                            
                    ?>
                    </select>
                    </br>
                    </br>
                    </form>