meta_tags.module

<?php
/**
* @file
* Lets users add private annotations to nodes.
*
* Adds a text field when a node is displayed
* so that authenticated users may make notes.
*/

/**
* Implementation of hook_menu().
*/

function meta_tags_menu() {
  $items['admin/config/meta_tags'] = array(
    'title' => 'Meta tags',
    'description' => 'Adjust Meta tags options.',
    'position' => 'right',
    'weight' => -5,
    'page callback' => 'system_admin_menu_block_page',
    'access arguments' => array('administer site configuration'),
    'file' => 'system.admin.inc',
    'file path' => drupal_get_path('module', 'system'),
  );
  
  $items['admin/config/meta_tags/settings'] = array(
    'title' => 'Meta tag settings',
    'description' => 'Set default meta information and select content types',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('meta_tags_admin_settings'),
    'access arguments' => array('administer site configuration'),
    'type' => MENU_NORMAL_ITEM,
    'file' => 'meta_tags.admin.inc',
  );
  return $items;
}


/**
 * the title needs to be set in a preprocess hook otherwise it's too late - Not sure about this but seems to work
 */
 
function meta_tags_preprocess_html(&$variables, $hook){
	$nodeId = arg(1);

	$titleNode = node_load($nodeId);
	
	if (isset($titleNode->meta_title['und'][0]['value'])) {
		$node_meta_title = $titleNode->meta_title['und'][0]['value'];
	} else {
		$node_meta_title = variable_get('meta_tags_default_title');
	}

	$variables['head_title'] = $node_meta_title; 	
	unset($titleNode->meta_title); 
	return $variables;
}

/**
* Implements hook_node_load()
*/
function meta_tags_node_load($nodes, $types) {
	foreach ($nodes as $node) {	
			
		// If there is content for description set for the node then use it, otherwise fallback to the defaults
		if (isset($node->meta_desc['und'][0]['value'])) {
			$node_meta_desc = $node->meta_desc['und'][0]['value'];
		} else {
			$node_meta_desc = variable_get('meta_tags_default_desc');
		}		
		
		// Keywords are added on to the end of the default keywords if they are set.		
		$node_default_keywords = variable_get('meta_tags_default_keywords');
		
		if (isset($node->meta_keywords['und'][0]['value'])) {
			$node_meta_keywords = $node->meta_keywords['und'][0]['value'];	
			$node_default_keywords .= ', ' . $node_meta_keywords;
		}	
		
		//drupal_set_message('Meta title node  - ' . $node->meta_desc['und'][0]['value'] . ', '.$node_meta_desc . ', '.$node_default_keywords, 'status');
		
		// Meta information is set up...		
		$meta_description = array(
			'#type' => 'html_tag',
			'#tag' => 'meta',
			'#attributes' => array(
				'name' => 'description',
				'content' =>  $node_meta_desc
			)
		);  
		
		// Meta information is set up...		
		$meta_keywords = array(
			'#type' => 'html_tag',
			'#tag' => 'meta',
			'#attributes' => array(
				'name' => 'keywords',
				'content' =>  $node_default_keywords
			)
		);  
				
		//... and then added to the header
		drupal_add_html_head($meta_description, 'meta_description');
		drupal_add_html_head($meta_keywords, 'meta_keywords');
		
		// The content	
		//unset($node->meta_title);	
		//unset($node->meta_desc);
		//unset($node->meta_keywords);
	}
}