Echo custom field value

Question

So I am customizing the [CPT Bootstrap Carousel plugin][1] to fit my needs. I have added custom field support to the custom post type, where the custom field is suppose to add a button on the carousel items. I have been able to register the custom field in the backend and the button is showing up on the Carousel items, but the href property is empty. I believe that the problem is in the custom loop or in the way I am using echo, but I can´t seam to figure it out. The area where I believe the problem in the code is have been market with <!--Possible problem-->.

Here is updated, functioning code: /PS: but have a look a phils answer, probably a more stable solution.

<?php
/*
Plugin Name: CPT Bootstrap Carousel
Plugin URI: http://www.tallphil.co.uk/bootstrap-carousel
Description: A custom post type for choosing images and content which outputs <a href="http://twitter.github.io/bootstrap/javascript.html#carousel" target="_blank">Bootstrap Carousel</a> from a shortcode. Requires Bootstrap javascript and CSS to be loaded separately.
Version: 1.1
Author: Phil Ewels
Author URI: http://phil.ewels.co.uk
License: GPLv2
*/

// Custom Post Type Setup
add_action( 'init', 'cptbc_post_type' );
function cptbc_post_type() {
$labels = array(
    'name' => 'Carousel Images',
    'singular_name' => 'Carousel Image',
    'add_new' => 'Add New',
    'add_new_item' => 'Add New Carousel Image',
    'edit_item' => 'Edit Carousel Image',
    'new_item' => 'New Carousel Image',
    'view_item' => 'View Carousel Image',
    'search_items' => 'Search Carousel Images',
    'not_found' =>  'No Carousel Image',
    'not_found_in_trash' => 'No Carousel Images found in Trash', 
    'parent_item_colon' => '',
    'menu_name' => 'Carousel'
);
$args = array(
    'labels' => $labels,
    'public' => true,
    'exclude_from_search' => true,
    'publicly_queryable' => false,
    'show_ui' => true, 
    'show_in_menu' => true,
    'query_var' => true,
    'rewrite' => true,
    'capability_type' => 'page',
    'has_archive' => true, 
    'hierarchical' => false,
    'menu_position' => 21,
    'supports' => array('title','excerpt','thumbnail', 'page-attributes', 'custom-fields')
); 
register_post_type('cptbc', $args);
}


// Add theme support for featured images if not already present
// http://wordpress.stackexchange.com/questions/23839/using-add-theme-support-inside-a-plugin
function cptbc_addFeaturedImageSupport() {
$supportedTypes = get_theme_support( 'post-thumbnails' );
if( $supportedTypes === false )
    add_theme_support( 'post-thumbnails', array( 'cptbc' ) );               
elseif( is_array( $supportedTypes ) ) {
    $supportedTypes[0][] = 'cptbc';
    add_theme_support( 'post-thumbnails', $supportedTypes[0] );
}
}
add_action( 'after_setup_theme', 'cptbc_addFeaturedImageSupport');

// FRONT END

// Shortcode
function cptbc_shortcode($atts, $content = null) {
// Set default shortcode attributes
$defaults = array(
    'interval' => '5000',
    'showcaption' => 'true',
    'showcontrols' => 'true'
);

// Parse incomming $atts into an array and merge it with $defaults
$atts = shortcode_atts($defaults, $atts);

return cptbc_frontend($atts);
}
add_shortcode('image-carousel', 'cptbc_shortcode');

// Display latest WftC
function cptbc_frontend($atts){
$id = rand(0, 999); // use a random ID so that the CSS IDs work with multiple on one page
$args = array( 'post_type' => 'cptbc', 'orderby' => 'menu_order', 'order' => 'ASC');
$loop = new WP_Query( $args );
$images = array();
while ( $loop->have_posts() ) {
    $loop->the_post();
    if ( '' != get_the_post_thumbnail() ) {
        $title = get_the_title();
        $content = get_the_excerpt();
        $image = get_the_post_thumbnail( get_the_ID(), 'full' );
        $link = get_post_custom_values('link');
        $images[] = array('title' => $title, 'content' => $content, 'image' => $image, 'link' => $link);
    }
}
if(count($images) > 0){
    ob_start();
    ?>
    <div id="cptbc_<?php echo $id; ?>" class="carousel slide">
        <ol class="carousel-indicators">
        <?php foreach ($images as $key => $image) { ?>
            <li data-target="#cptbc_<?php echo $id; ?>" data-slide-to="<?php echo $key; ?>" data-interval="<?php echo $atts['interval']; ?>" <?php echo $key == 0 ? 'class="active"' : ''; ?>></li>
        <?php } ?>
        </ol>
        <div class="carousel-inner">
        <?php foreach ($images as $key => $image) { ?>
            <div class="item <?php echo $key == 0 ? 'active' : ''; ?>">
                <?php echo $image['image']; ?>
                <?php if($atts['showcaption'] === 'true') { ?>
                    <div class="carousel-caption">
                        <h2><?php echo $image['title']; ?></h2>
                        <p class="lead"><?php echo $image['content']; ?></p>
                        <?php echo '<a class="btn btn-large btn-primary" href="' . $image['link'][0] . '">Läs mer</a>';?>
                    </div>
                <?php } ?>
            </div>
        <?php } ?>
        </div>
        <?php if($atts['showcontrols'] === 'true') { ?>
            <a class="left carousel-control" href="#cptbc_<?php echo $id; ?>" data-slide="prev">‹</a>
            <a class="right carousel-control" href="#cptbc_<?php echo $id; ?>" data-slide="next">›</a>
        <?php } ?>
    </div>
<?php }
$output = ob_get_contents();
ob_end_clean();

// Restore original Post Data
wp_reset_postdata();    

return $output;
}

// Call the carousel in javascript, else it won't start scrolling on its own
function cptbc_footer_js() {
?>
<script type="text/javascript">
jQuery(function(){
    jQuery('.carousel').carousel()
});
</script>
<?php
}
add_action('wp_footer', 'cptbc_footer_js');

?>

Answer 1

Repost for any future googlers from @StenW 's wordpress plugin support thread:

Github user @atnon made a very similar modification to the code 10 days ago, also using custom-fields (though giving the image a link rather than putting a link in the caption). You can see this code in his pull request.

I re-wrote his code and released an update to the plugin last night, so if you're happy with just the image having a link you should be able to do that with the update.

If I were you, I'd update the plugin to incorporate my new code and then make a small edit just to change where the link is being printed in the output. That way you get a cleaner meta-box instead of relying on custom fields and it should work without much debugging.

Example modification (untested):

<div class="item <?php echo $key == 0 ? 'active' : ''; ?>">
    <?php echo $image['image'];
    if($atts['showcaption'] === 'true') { ?>
        <div class="carousel-caption">
            <h4><?php echo $image['title']; ?></h4>
            <p><?php echo $image['content']; ?></p>
            <?php if($image['url']) {
                echo '<a href="'.$image['url'].'"';
                if($image['url_openblank']) {
                    echo ' target="_blank"';
                }
                echo '>Läs mer</a>';
            } ?>
        </div>
    <?php } ?>
</div>

Answer 2

Use:

$link = get_post_meta($post->ID, 'link', TRUE); // please, note true

If you use, instead

get_post_meta($post->ID, 'link', FALSE);

an array is returned so you should use

href="' . $image['link'][0] . '"

See the codex for get_post_meta