If post custom meta data is not set, show normal state

Question

I'm much of a php-noob but have this idea of a loop for my site. I have the idea behind it but maybe you have an idea how to put this into code:

$customfield = get_specific_customfield

if $custom-field is = not empty
echo 'custom-field-input" class="'

else

echo '`<?php echo $thumbnail_src[0]; ?>" class="fancybox`'

(I have to integrate the fancy-box stuff to control how the input will be displayed)

Answer 1

To get a value of a single custom field use

<?php
    $post_id = $post->ID;
    $key = 'value';  // change value to what custom field you are looking for
    // To retrieve only the first value of given key
    $customfield = get_post_meta($post_id, $key, 'true');
    // To use as default
    $customfield = get_post_meta($post_id, $key);
    // Then check what you got
    if($customfield)
?>
    <img class="thumb" src="<?php echo get_post_meta($post_id, $key, true) ?>" alt="<?php the_title(); ?>" />
<?php
    else

    echo 'whatever you want to show by default';
?>

For further reading goto codex

Hope it helps you