EntityMalformedException when retrieving Drupal 7 custom field - exception

Question

I am playing with Drupal and I am trying to add a second line to the site slogan.
The following is the piece of page.tpl.php where I am working.
<?php if ($site_name || $site_slogan): ?>
<div id="name-and-slogan" class="hgroup">
<?php if ($site_name): ?>
<h1 class="site-name">
<a href="<?php print $front_page; ?>" title="<?php print t('Home'); ?>">
<?php print $site_name; ?>
</a>
</h1>
<?php endif; ?>
<?php if ($site_slogan): ?>
<p class="site-slogan"><?php print $site_slogan; ?></p>
<?php endif; ?>
<?php
/* ADDED */
$node = menu_get_object();
$siteslogan2 = field_get_items('node', $node, 'field_siteslogan2');
?>
<?php if ($siteslogan2): ?>
<p class="site-slogan2"><?php print $siteslogan2; ?></p>
<?php endif; ?>
</div>
<?php endif; ?>
I basically added a new Content Type with a field called siteslogan2 (field_siteslogan2) and now I would like to retrieve and show it here.
The first problem is that the $node var is not defined (even if according to the documentation it should be). The second problem is that I receive EntityMalformedException: Missing bundle property on entity of type node. in entity_extract_ids() when I define it manually and run it.
First of all, is this the right approach to the problem? Secondly, why do I receive the EntityMalformedException and how can I fix it?
var_dump($node) produces NULL. It must be the way I get the $node content that is not good. The doc is a bit cryptic to me when it says:
$node: The node object, if there is an automatically-loaded node associated with the page, and the node ID is the second argument in the page's path (e.g. node/12345 and node/12345/revisions, but not comment/reply/12345).

Answer 1

This sort of thing is can be done using a preprocessing function in your theme's template.php to define and set a variable in the $varables array.
This variable then becomes available to whichever template ( page, node, form, etc ) you have done the preprocessing on. Your theme's template.php file will most likely have comments on how to do this.
for instance, doing this in the template.php creates or modifies the value of the variable $display_header, making it available for use in node.tpl.php
function yourthemename_preprocess_node(&$variables, $hook) {
$variables['display_header'] = false;
}
You can then modify the node template file to use this variable.
For something simple like a sub-slogan, you can add a setting to the theme, so it shows up on the theme's configuration page like any other theme setting.
This requires implementing this function in your theme's theme-settings.php:
function yourthemename_form_system_theme_settings_alter(&$form, $form_state) {}
This provides information to the settings form regarding the new setting. like this:
https://api.drupal.org/api/drupal/modules!system!theme.api.php/function/hook_form_system_theme_settings_alter/7
Hopefully that's enough to get you started.