How do I implement hook_page_alter() in a module?

Question

I'm trying to add a piece on content to the $page['content'] variable, but it's just not working and the examples are not helping me. My code is the following:

function my_modulename_page_alter(&$page) {
    $page['content'] = $extracontent . $page['content'];
}

dpm() doesn't allow me to see the available variables. What am I doing wrong?

Answer 1

Try using hook_page_build(&$page). hook_page_alter(&$page), which is called directly after it, is meant for themers to use after all the modules are finished with their business.

I just implemented function MODULE_page_alter(&$page), and it worked in the module as expected.
Did you clear the cache so the module is registered?

Answer 2

$page['content'] is not a string, but an array that contains many indexes. As reported in hook_page_alter(), the 'content' element contains the main content of the current page, and its structure will vary depending on what module is responsible for building the page.

When the page is build from the Node and Blog modules, $page['content'] contains:

• $page['content']['system_main']['nodes'][$nid]['body']: the node body
• $page['content']['system_main']['nodes'][$nid]['links']: the array of links attached to the node
• $page['content']['system_main']['nodes'][$nid]['#node']: the node object
• $page['content']['system_main']['pager']: the pager for the results.

Answer 3

For me, it's accessed at $page['content']['system_main']['nodes'][$nid][<fieldname>]. I've been wondering if it can also be accessed with hook_node_view_alter().

As for dpm(), it does 2 weird things for me:

• It doesn't work on $page, but does on a sub-element such as $page['content'].
• You have to click on another page for it to display. An answer at https://stackoverflow.com/questions/5271671/drupal-understanding-how-to-print-variables explains why it only appears on a subsequent page. It appears for me by clicking on Admin->Configuration->Development->Performance afterwards. (I put a link to it in the Admin Shortcuts bar.)