Drupal 7 Module Development

Chapter 3
By the way, does your brain hurt yet? You may want to take a break now; go out and
get some air, or, at the very least, have a strong drink handy when you start reading
the next section.
Render elements
Render elements are new to Drupal 7's theme layer. They've existed since Drupal 4.7
as part of the Form API, but they've now been injected into the heart of the theme
system. A Render element is a complex data structure passed as a single parameter
to theme(), as one of its variables. Render elements are fundamentally nested arrays
that can include:
• The data to be rendered
• Other render elements which are considered "children" of the element
• An array of structures such as CSS and JavaScript files, that should be
attached to the page when it is rendered
• A list of theme hooks that can be used to theme the data
• A list of callback functions to run on the element before and after it
is themed
In template files, render elements are handled slightly differently then normal
variables, using the syntax we saw earlier in our typical-hook.tpl.php example:
In theme functions, render elements are included with its output using the
drupal_render() function:
$output .= drupal_render($element);
Let's look at a simple render element:
$element = array(
'#prefix' => '',
'#markup' => '' . t('There is no spoon.') . '',
'#suffix' => '',
);
In the preceding render element our main property is the #markup property which
uses a string containing HTML markup as-is for the rendered element. The other
properties do exactly what they hint at, prepending or appending HTML markup
to the rendered element. If drupal_render($element) was called, it would simply
return the three strings concatenated together.
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