The following will add 1 extra meta box to your (insert-edit) page.
In it you can add custom fields to save.
It does not switch depending on the selected template.
I would recomend using javascript to show/hide fields to do this. Based on ID of the <p>
If you get the meta box working with ALL possible fields you can show I'm willing to help with the javascript to hide and show based on the template.
GL
<?php
add_action( 'add_meta_boxes', 'carrousel_build' );
function carrousel_build()
{
add_meta_box('carrousel', 'Carrousel opties', 'carrousel_options', 'page',/*show on 'pages'*/ 'normal', 'high');
}
//this will add a meta box with custom fields
function carrousel_options ($post)
{ ?>
<p>
Description
</p>
<p id="field1_container">
<label for="field1">Custom field 1</label>
<br/>
<input type="text" id="field1" name="field1" value="<?php echo get_post_meta($post->ID, 'field1', true) ?>" size="25" />
</p>
<p id="field2_container">
<label for="field2">Custom field 2</label>
<br/>
<input type="text" id="field2" name="field2" value="<?php echo get_post_meta($post->ID, 'field2', true) ?>" size="25" />
</p>
<?php }
//save the values of the meta box
add_action( 'save_post', 'post_save' );
function post_save($post_id)
{
// Check permissions
if (isset ($_POST['post_type']) && 'carrousel' == $_POST['post_type'] && !current_user_can( 'edit_page', $post_id ))
{
return;
}
if (isset($_POST['field1'])) {
$subtitle = $_POST['field1'];
update_post_meta($post_id, 'field1', $subtitle);
}
if (isset($_POST['field2']))
{
$link = $_POST['field2'];
update_post_meta($post_id, 'field2', $link);
}
}