ID an PopUp übergeben

<?php


/**
* Registriert den Post Type „product“
*/
function register_product_post_type() {
    $labels = array(
        'name'                  => __( 'Produkte', TRANSLATION_CONST ),
        'singular_name'         => __( 'Produkt', TRANSLATION_CONST ),
        'add_new'               => __( 'Hinzufügen', TRANSLATION_CONST ),
        'add_new_item'          => __( 'Produkt hinzufügen', TRANSLATION_CONST ),
        'edit_item'             => __( 'Produkt bearbeiten', TRANSLATION_CONST ),
        'new_item'              => __( 'Produkt hinzufügen', TRANSLATION_CONST ),
        'view_item'             => __( 'Produkt anzeigen', TRANSLATION_CONST ),
        'view_items'             => __( 'Produkte anzeigen', TRANSLATION_CONST ),
        'search_items'          => __( 'Produkt suchen', TRANSLATION_CONST ),
        'not_found'             => __( 'Keine Produkte gefunden', TRANSLATION_CONST ),
        'not_found_in_trash'    => __( 'Keine Produkte im Papierkorb gefunden', TRANSLATION_CONST ),
        'parent_item_colon'     => __( 'Übergeordnete Produkte:', TRANSLATION_CONST ),
        'all_items'             => __( 'Alle Produkte:', TRANSLATION_CONST ),
        'archives'              => __( 'Produkt Archiv:', TRANSLATION_CONST ),
        'attributes'            => __( 'Produkt Attribute:', TRANSLATION_CONST ),
        'insert_into_item'      => __( 'Zum Produkt hinzufügen', TRANSLATION_CONST ),
        'uploaded_to_this_item' => __( 'Zum Produkt hinzugefügt', TRANSLATION_CONST ),
        'featured_image'        => __( 'Produktbild', TRANSLATION_CONST ),
        'set_featured_image'    => __( 'Produktbild setzen:', TRANSLATION_CONST ),
        'remove_featured_image' => __( 'Produktbild entfernen:', TRANSLATION_CONST ),
        'use_featured_image'    => __( 'Als Produktbild verwenden:', TRANSLATION_CONST ),
        'menu_name'             => __( 'Produkte', TRANSLATION_CONST ),
    );
 
    $supports = array(
        'title',
        'editor', // Content Bereich
        'excerpt', // Kurzer Auszug des Contents für Archivseiten
        'author',
        'thumbnail', // featured_image / Produktbild
        //'trackbacks',
        'custom-fields',
        //'revisions',
        'page-attributes',
        'comments'
    );
 
    $args = array(
        'labels' => $labels,
        'hierarchical' => false,
        'description' => __( 'Produkte für mein eigenes E-Commerce Plugin', TRANSLATION_CONST ),
        'supports' => $supports,
        'public' => true,
        'show_ui' => true,
        'show_in_menu' => true,
        'menu_position' => 5, // Unterhalb der Posts
        'menu_icon' => 'dashicons-card',
        'show_in_nav_menus' => true,
        'publicly_queryable' => true,
        'exclude_from_search' => false,
        'has_archive' => true,
        'query_var' => true,
        'can_export' => true,
        'capability_type' => 'post'
    );
 
    register_post_type( 'product', $args );
}
add_action( 'init', 'register_product_post_type' );




function product_post_type_add_meta_boxes( $post ){
    add_meta_box( 'price_meta_box',
        'Price Detail',
        'product_post_type_build_price_meta_box',
        'product', 'normal', 'high'
    );
}
add_action( 'add_meta_boxes_product', 'product_post_type_add_meta_boxes' );


function product_post_type_build_price_meta_box($post) {
    wp_nonce_field( basename( __FILE__ ), 'product_post_type_price_meta_box_nonce' );


    $current_price = get_post_meta( $post->ID, 'product_price', true );
    ?>
    <div class="inside">
        <section id="price-meta-box-container">
            <p>
                <input type="number" name="product_price" id="product-price"<?php echo ' value="'.$current_price.'"'; ?>>
            </p>
        </section>
    </div>
    <?php
}


function product_post_type_save_price_meta_boxes_data( $post_id ){
    if ( !isset( $_POST['product_post_type_price_meta_box_nonce'] ) ||
            !wp_verify_nonce(
                $_POST['product_post_type_price_meta_box_nonce'],
                basename( __FILE__ )
            ) ){
        return;
    }


    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
        return;


    if ( defined( 'DOING_AJAX' ) && DOING_AJAX )
        return;


    if ( !current_user_can( 'edit_post', $post_id ) )
        return;


    if ( isset( $_REQUEST['product_price'] ) ) {
        update_post_meta(
            $post_id,
            'product_price',
            sanitize_text_field( $_POST['product_price'] )
        );
    }
}
add_action( 'save_post_product', 'product_post_type_save_price_meta_boxes_data', 10, 2 );


function the_product_price($post = 0, $echo = true) {
    $post = get_post( $post );


    $id = isset( $post->ID ) ? $post->ID : 0;
    $value = get_post_meta( $id, 'product_price', true );


    if($echo) {
        echo sprintf(
            '<span class="product-detail--price">%s %s</span>',
            esc_html($value),
            __('€', TRANSLATION_CONST)
        );
    }
    else
        return $value;
}

<?php
/**
 * Template Name: Archive Product Template
 *
 * Description: Eine eigene Archivseite für meinen Post Type „product“
 */


get_header(); ?>


    <div class="main-wrap" role="main">


        <!-- Darstellung der Produkte -->
        <section id="product-listing">
            <?php if ( have_posts() ) : ?>
                <div class="row">
                <?php while ( have_posts() ) : the_post(); ?>
                    <div class="column"">
           <?php get_template_part( 'product-content', get_post_format() ); ?>
        </div>
                <? endwhile; ?>
                </div>
            <?php endif; ?>
        </section>


    </div>


<?php get_footer();

<?php
/**
 * Das Standard-Template zum Anzeigen eines Produktes
 */
?>


<div class="product-container" id="product-<?php the_ID(); ?>">
    <?php if ( has_post_thumbnail() ) : ?>
    <a href="<?php the_permalink(); ?>">
         <img src="<?php the_post_thumbnail_url( ); ?>">
    </a>
    <?php endif; ?>


    <div class="product-content-section">
        <header>
            <h3><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h3>
        </header>
        <div class="entry-content">
            <?php
                the_product_price(get_the_ID());
                echo '<br />';
                the_excerpt();
            ?>


        </div>
    </div>
</div>

<?php get_header(); ?>


<?php while ( have_posts() ) : the_post(); ?>
<article <?php post_class() ?> id="product-<?php the_ID(); ?>">
    <div class="row column" id="product-header">
        <h1 class="entry-title"><?php the_title(); ?></h1>
    </div>


    <div class="main-wrap" role="main">
        <div class="entry-content">
            <div class="row">
                <div class="medium-6 columns">
                    <?php if(has_post_thumbnail( )) : ?>
                        <a href="<?php the_post_thumbnail_url('large'); ?>">
                                <img src="<?php the_post_thumbnail_url('large'); ?>"/>
                        </a>
                    <?php endif; ?>
                </div>
                <div class="medium-6 columns">
                    <?php the_product_price(get_the_ID()); ?>
                </div>
            </div>


            <div class="row columns">
                <?php the_content(); ?>
            </div>
        </div>


        <footer>
            <?php
                wp_link_pages(
                    array(
                        'before' => '<nav id="page-nav"><p>' . __( 'Produkte:', TRANSLATION_CONST ),
                        'after'  => '</p></nav>',
                    )
                );
            ?>
        </footer>


        <!-- Das ist das mit dem Kommentar kram -->   
        <?php comments_template(); ?>


    </div>
</article>
<?php endwhile;?>


<?php get_footer();