Marcus Povey <marcus@dushka.co.uk>

* Added caching to entities. Please report any problems.

git-svn-id: https://code.elgg.org/elgg/trunk@831 36083f99-b078-4883-b0ff-0f9b5a30f544

1 files changed, 381 insertions, 271 deletions

diff --git a/engine/lib/entities.php b/engine/lib/entities.php
index db3665c6f..cbcd5ccad 100644
--- a/engine/lib/entities.php
+++ b/engine/lib/entities.php
@@ -11,6 +11,9 @@
 	 * @link http://elgg.org/
 	 */
 
+	/// Cache objects in order to minimise database access.
+	$ENTITY_CACHE = array();
+	
 	/**
 	 * ElggEntity The elgg entity superclass
 	 * This class holds methods for accessing the main entities table.
@@ -32,7 +35,11 @@
 		 * Subclasses should add to this in their constructors.
 		 * Any field not appearing in this will be viewed as a 
 		 */
-		protected $attributes;

+		protected $attributes;
+
+		/**
+		 * Temporary cache for metadata, permitting meta data access before a guid has obtained.
+		 */
 		protected $temp_metadata;
 				
 		/**
@@ -45,9 +52,11 @@
 		 */
 		protected function initialise_attributes()
 		{
+			initialise_entity_cache();
+
 			// Create attributes array if not already created
 			if (!is_array($this->attributes)) $this->attributes = array();
-			if (!is_array($this->temp_metadata)) $this->temp_metadata = array();

+			if (!is_array($this->temp_metadata)) $this->temp_metadata = array();
 			
 			$this->attributes['guid'] = "";
 			$this->attributes['type'] = "";
@@ -77,14 +86,14 @@
 				return $this->attributes[$name];
 			}
 			
-			// No, so see if its in the meta data for this entity

+			// No, so see if its in the meta data for this entity
 			if ((int) ($this->guid) > 0) {
 				$meta = $this->getMetaData($name);
 				if ($meta)
-					return $meta;

-			} else {

-				if (isset($this->temp_metadata[$name]))

-					return $this->temp_metadata[$name];

+					return $meta;
+			} else {
+				if (isset($this->temp_metadata[$name]))
+					return $this->temp_metadata[$name];
 			}
 			
 			// Can't find it, so return null
@@ -117,9 +126,9 @@
 				$this->attributes[$name] = $value;
 			}
 			else if ((int) $this->guid > 0) {
-				return $this->setMetaData($name, $value);

-			} else {

-				$this->temp_metadata[$name] = $value;

+				return $this->setMetaData($name, $value);
+			} else {
+				$this->temp_metadata[$name] = $value;
 			}
 			
 			return true;
@@ -135,9 +144,9 @@
 			$md = get_metadata_byname($this->getGUID(), $name);
 
 			if ($md && !is_array($md)) {
-				return $md->value;

-			} else if ($md && is_array($md)) {

-				return metadata_array_to_values($md);

+				return $md->value;
+			} else if ($md && is_array($md)) {
+				return metadata_array_to_values($md);
 			}
 				
 			return null;
@@ -155,11 +164,11 @@
 		public function setMetaData($name, $value, $value_type = "", $multiple = false)
 		{
 			if (is_array($value))
-			{

-				remove_metadata($this->getGUID(), $name);

+			{
+				remove_metadata($this->getGUID(), $name);
 				$multiple = true;
 				foreach ($value as $v) {
-					if (!create_metadata($this->getGUID(), $name, $v, $value_type, $this->getOwner(), $this->getAccessID(), $multiple)) return false; 

+					if (!create_metadata($this->getGUID(), $name, $v, $value_type, $this->getOwner(), $this->getAccessID(), $multiple)) return false; 
 				}
 					
 				return true;
@@ -172,24 +181,24 @@
 		 * Clear metadata.
 		 */
 		public function clearMetaData($name = "")
-		{

+		{
 			if (empty($name)) {
-				return clear_metadata($this->getGUID());

-			} else {

-				return remove_metadata($this->getGUID(),$name);

+				return clear_metadata($this->getGUID());
+			} else {
+				return remove_metadata($this->getGUID(),$name);
 			}
 		}
-		

-		/**

-		 * Remove all entities associated with this entity

-		 *

-		 * @return true

-		 */

-		public function clearRelationships() {

-			remove_entity_relationships($this->getGUID());

-			remove_entity_relationships($this->getGUID(),"",true);

-			return true;

-		}

+		
+		/**
+		 * Remove all entities associated with this entity
+		 *
+		 * @return true
+		 */
+		public function clearRelationships() {
+			remove_entity_relationships($this->getGUID());
+			remove_entity_relationships($this->getGUID(),"",true);
+			return true;
+		}
 		
 		/**
 		 * Adds an annotation to an entity. By default, the type is detected automatically; however, 
@@ -277,39 +286,39 @@
 		{
 			return get_annotations_max($this->getGUID(), "","",$name);
 		}
-		

-		/**

-		 * Gets an array of entities from a specific relationship type

-		 *

-		 * @param string $relationship Relationship type (eg "friends")

-		 * @param true|false $inverse Is this an inverse relationship?

-		 * @param int $limit Number of elements to return

-		 * @param int $offset Indexing offset

-		 * @return array|false An array of entities or false on failure

-		 */		

-		function getEntitiesFromRelationship($relationship, $inverse = false, $limit = 50, $offset = 0) {

-			return get_entities_from_relationship($relationship,$this->getGUID(),$inverse,"","","","time_created desc",$limit,$offset);			

-		}

-		

-		/**

-		 * Gets the number of of entities from a specific relationship type

-		 *

-		 * @param string $relationship Relationship type (eg "friends")

-		 * @return int|false The number of entities or false on failure

-		 */		

-		function countEntitiesFromRelationship($relationship) {

-			return get_entities_from_relationship($relationship,$this->getGUID(),false,"","","","time_created desc",null,null,true);			

-		}

-		

-		/**

-		 * Determines whether or not the specified user (by default the current one) can edit the entity 

-		 *

-		 * @param int $user_guid The user GUID, optionally (defaults to the currently logged in user)

-		 * @return true|false

-		 */

-		function canEdit($user_guid = 0) {

-			return can_edit_entity($this->getGUID(),$user_guid);

-		}

+		
+		/**
+		 * Gets an array of entities from a specific relationship type
+		 *
+		 * @param string $relationship Relationship type (eg "friends")
+		 * @param true|false $inverse Is this an inverse relationship?
+		 * @param int $limit Number of elements to return
+		 * @param int $offset Indexing offset
+		 * @return array|false An array of entities or false on failure
+		 */		
+		function getEntitiesFromRelationship($relationship, $inverse = false, $limit = 50, $offset = 0) {
+			return get_entities_from_relationship($relationship,$this->getGUID(),$inverse,"","","","time_created desc",$limit,$offset);			
+		}
+		
+		/**
+		 * Gets the number of of entities from a specific relationship type
+		 *
+		 * @param string $relationship Relationship type (eg "friends")
+		 * @return int|false The number of entities or false on failure
+		 */		
+		function countEntitiesFromRelationship($relationship) {
+			return get_entities_from_relationship($relationship,$this->getGUID(),false,"","","","time_created desc",null,null,true);			
+		}
+		
+		/**
+		 * Determines whether or not the specified user (by default the current one) can edit the entity 
+		 *
+		 * @param int $user_guid The user GUID, optionally (defaults to the currently logged in user)
+		 * @return true|false
+		 */
+		function canEdit($user_guid = 0) {
+			return can_edit_entity($this->getGUID(),$user_guid);
+		}
 		
 		/**
 		 * Enter description here...
@@ -334,13 +343,13 @@
 		 * @todo document me
 		 */
 		public function getOwner() { return $this->get('owner_guid'); }
-		

-		/**

-		 * Returns the actual entity of the user who owns this entity, if any

-		 *

-		 * @return ElggEntity The owning user

-		 */

-		public function getOwnerEntity() { return get_entity($this->get('owner_guid')); }

+		
+		/**
+		 * Returns the actual entity of the user who owns this entity, if any
+		 *
+		 * @return ElggEntity The owning user
+		 */
+		public function getOwnerEntity() { return get_entity($this->get('owner_guid')); }
 		
 		/**
 		 * Enter description here...
@@ -373,13 +382,13 @@
 		 * @todo document me
 		 */
 		public function getTimeUpdated() { return $this->get('time_updated'); }
-		

-		/**

-		 * Gets the display URL for this entity

-		 *

-		 * @return string The URL

-		 */

-		public function getURL() { return get_entity_url($this->getGUID()); }

+		
+		/**
+		 * Gets the display URL for this entity
+		 *
+		 * @return string The URL
+		 */
+		public function getURL() { return get_entity_url($this->getGUID()); }
 		
 		/**
 		 * Save generic attributes to the entities table.
@@ -389,6 +398,8 @@
 			$guid = (int) $this->guid;
 			if ($guid > 0)
 			{ 
+				cache_entity($this);
+
 				return update_entity(
 					$this->get('guid'),
 					$this->get('owner_guid'),
@@ -399,14 +410,17 @@
 			{ 
 				$this->attributes['guid'] = create_entity($this->attributes['type'], $this->attributes['subtype'], $this->attributes['owner_guid'], $this->attributes['access_id']); // Create a new entity (nb: using attribute array directly 'cos set function does something special!)
 				if (!$this->attributes['guid']) throw new IOException(elgg_echo('IOException:BaseEntitySaveFailed')); 
-				

-				// Save any unsaved metadata

-				if (sizeof($this->temp_metadata) > 0) {

-					foreach($this->temp_metadata as $name => $value) {

-						$this->$name = $value;

-						unset($this->temp_metadata[$name]);

-					}

-				}

+				
+				// Save any unsaved metadata
+				if (sizeof($this->temp_metadata) > 0) {
+					foreach($this->temp_metadata as $name => $value) {
+						$this->$name = $value;
+						unset($this->temp_metadata[$name]);
+					}
+				}
+				
+				// Cache object handle
+				if ($this->attributes['guid']) cache_entity($this); 
 				
 				return $this->attributes['guid'];
 			}
@@ -431,6 +445,9 @@
 				foreach($objarray as $key => $value) 
 					$this->attributes[$key] = $value;
 				
+				// Cache object handle
+				if ($this->attributes['guid']) cache_entity($this); 
+					
 				return true;
 			}
 			
@@ -442,7 +459,7 @@
 		 */
 		public function delete() 
 		{ 
-			$res = delete_entity($this->get('guid'));

+			$res = delete_entity($this->get('guid'));
 			return $res;
 		}
 
@@ -631,6 +648,83 @@
 	}
 
 	/**
+	 * Initialise the entity cache.
+	 */
+	function initialise_entity_cache()
+	{
+		global $ENTITY_CACHE;
+		
+		if (!is_array($ENTITY_CACHE))
+			$ENTITY_CACHE = array();
+	}
+	
+	/**
+	 * Invalidate this class' entry in the cache.
+	 * 
+	 * @param int $guid The guid
+	 */
+	function invalidate_cache_for_entity($guid)
+	{
+		global $ENTITY_CACHE;
+		
+		$guid = (int)$guid;
+			
+		unset($ENTITY_CACHE[$guid]);
+				
+	}
+	
+	/**
+	 * Cache an entity.
+	 * 
+	 * @param ElggEntity $entity Entity to cache
+	 */
+	function cache_entity(ElggEntity $entity)
+	{
+		global $ENTITY_CACHE;
+		
+		$ENTITY_CACHE[$entity->guid] = &$entity;
+	}
+	
+	/**
+	 * Retrieve a entity from the cache.
+	 * 
+	 * @param int $guid The guid
+	 */
+	function retrieve_cached_entity($guid)
+	{
+		global $ENTITY_CACHE;
+		
+		$guid = (int)$guid;
+			
+		if (isset($ENTITY_CACHE[$guid])) 
+			return $ENTITY_CACHE[$guid];
+				
+		return false;
+	}
+	
+	/**
+	 * As retrieve_cached_entity, but returns the result as a stdClass (compatible with load functions that
+	 * expect a database row.)
+	 * 
+	 * @param int $guid The guid
+	 */
+	function retrieve_cached_entity_row($guid)
+	{
+		$obj = retrieve_cached_entity($guid);
+		if ($obj)
+		{
+			$tmp = new stdClass;
+			
+			foreach ($obj as $k => $v)
+				$tmp->$k = $v;
+				
+			return $tmp;
+		}
+
+		return false;
+	}
+	
+	/**
 	 * Return the integer ID for a given subtype, or false.
 	 * 
 	 * TODO: Move to a nicer place?
@@ -756,11 +850,11 @@
 		$owner_guid = (int)$owner_guid;
 		$access_id = (int)$access_id;
 		$time = time();
-		

-		$entity = get_entity($guid);

+		
+		$entity = get_entity($guid);
 		
 		if ($entity->canEdit()) {
-			

+			
 			if (trigger_event('update',$entity->type,$entity)) {
 				$ret = update_data("UPDATE {$CONFIG->dbprefix}entities set owner_guid='$owner_guid', access_id='$access_id', time_updated='$time' WHERE guid=$guid");
 				
@@ -768,9 +862,9 @@
 				if ($ret===false)
 					return false;
 
-				return true;

+				return true;
 			}
-			

+			
 		}
 	}
 	
@@ -780,7 +874,7 @@
 	 * @param string $type The type of the entity (site, user, object).
 	 * @param string $subtype The subtype of the entity.
 	 * @param int $owner_guid The GUID of the object's owner.
-	 * @param int $access_id The access control group to create the entity with.

+	 * @param int $access_id The access control group to create the entity with.
 	 * @param int $site_guid The site to add this entity to. Leave as 0 (default) for the current site.
 	 * @return mixed The new entity's GUID, or false on failure
 	 */
@@ -792,13 +886,13 @@
 		$subtype = add_subtype($type, $subtype);
 		$owner_guid = (int)$owner_guid; 
 		$access_id = (int)$access_id;
-		$time = time();

-		if ($site_guid == 0)

-			$site_guid = $CONFIG->site_guid;

+		$time = time();
+		if ($site_guid == 0)
+			$site_guid = $CONFIG->site_guid;
 		$site_guid = (int) $site_guid;
 					
-		if ($type=="") throw new InvalidParameterException(elgg_echo('InvalidParameterException:EntityTypeNotSet'));

-

+		if ($type=="") throw new InvalidParameterException(elgg_echo('InvalidParameterException:EntityTypeNotSet'));
+
 		return insert_data("INSERT into {$CONFIG->dbprefix}entities (type, subtype, owner_guid, site_guid, access_id, time_created, time_updated) values ('$type',$subtype, $owner_guid, $site_guid, $access_id, $time, $time)"); 
 	}
 	
@@ -815,9 +909,25 @@
 		
 		$guid = (int) $guid;
 		
-		$access = get_access_sql_suffix();
+		$row = retrieve_cached_entity_row($guid);
+		if ($row)
+		{
+			// We have already cached this object, so retrieve its value from the cache
+			if ($CONFIG->debug)
+				error_log("** Retrieving GUID:$guid from cache");
+
+			return $row;
+		}
+		else
+		{	
+			// Object not cached, load it.
+			if ($CONFIG->debug)
+				error_log("** GUID:$guid loaded from DB");
+			
+			$access = get_access_sql_suffix();
 		
-		return get_data_row("SELECT * from {$CONFIG->dbprefix}entities where guid=$guid and $access");
+			return get_data_row("SELECT * from {$CONFIG->dbprefix}entities where guid=$guid and $access");
+		}
 	}
 	
 	/**
@@ -876,8 +986,8 @@
 	 * @param int $owner_guid The GUID of the owning user
 	 * @param string $order_by The field to order by; by default, time_created desc
 	 * @param int $limit The number of entities to return; 10 by default
-	 * @param int $offset The indexing offset, 0 by default

-	 * @param boolean $count Set to true to get a count rather than the entities themselves (limits and offsets don't apply in this context). Defaults to false.

+	 * @param int $offset The indexing offset, 0 by default
+	 * @param boolean $count Set to true to get a count rather than the entities themselves (limits and offsets don't apply in this context). Defaults to false.
 	 * @param int $site_guid The site to get entities for. Leave as 0 (default) for the current site; -1 for all sites. 
 	 */
 	function get_entities($type = "", $subtype = "", $owner_guid = 0, $order_by = "time_created desc", $limit = 10, $offset = 0, $count = false, $site_guid = 0)
@@ -888,13 +998,13 @@
 			return false;
 		
 		$type = sanitise_string($type);
-		$subtype = get_subtype_id($type, $subtype);

+		$subtype = get_subtype_id($type, $subtype);
 		
 		$order_by = sanitise_string($order_by);
 		$limit = (int)$limit;
-		$offset = (int)$offset;

-		$site_guid = (int) $site_guid;

-		if ($site_guid == 0)

+		$offset = (int)$offset;
+		$site_guid = (int) $site_guid;
+		if ($site_guid == 0)
 			$site_guid = $CONFIG->site_guid;
 				
 		$where = array();
@@ -903,37 +1013,37 @@
 			$where[] = "type='$type'";
 		if ($subtype!=="")
 			$where[] = "subtype=$subtype";
-		if ($owner_guid != "") {

-			if (!is_array($owner_guid)) {

+		if ($owner_guid != "") {
+			if (!is_array($owner_guid)) {
 				$owner_guid = (int) $owner_guid;
-				$where[] = "owner_guid = '$owner_guid'";

-			} else if (sizeof($owner_guid) > 0) {

-				// Cast every element to the owner_guid array to int

-				$owner_guid = array_map("sanitise_int", $owner_guid);

-				$owner_guid = implode(",",$owner_guid);

-				$where[] = "owner_guid in ({$owner_guid})";

-			}

-		}

-		if ($site_guid > 0)

+				$where[] = "owner_guid = '$owner_guid'";
+			} else if (sizeof($owner_guid) > 0) {
+				// Cast every element to the owner_guid array to int
+				$owner_guid = array_map("sanitise_int", $owner_guid);
+				$owner_guid = implode(",",$owner_guid);
+				$where[] = "owner_guid in ({$owner_guid})";
+			}
+		}
+		if ($site_guid > 0)
 			$where[] = "site_guid = {$site_guid}";
-

+
 		if (!$count) {
-			$query = "SELECT * from {$CONFIG->dbprefix}entities where ";

-		} else {

-			$query = "select count(guid) as total from {$CONFIG->dbprefix}entities where ";

+			$query = "SELECT * from {$CONFIG->dbprefix}entities where ";
+		} else {
+			$query = "select count(guid) as total from {$CONFIG->dbprefix}entities where ";
 		}
 		foreach ($where as $w)
 			$query .= " $w and ";
-		$query .= get_access_sql_suffix(); // Add access controls

-		if (!$count) {

-			$query .= " order by $order_by";

+		$query .= get_access_sql_suffix(); // Add access controls
+		if (!$count) {
+			$query .= " order by $order_by";
 			if ($limit) $query .= " limit $offset, $limit"; // Add order and limit
 
-			$dt = get_data($query, "entity_row_to_elggstar");

-			return $dt;

-		} else {

-			$total = get_data_row($query);

-			return $total->total;

+			$dt = get_data($query, "entity_row_to_elggstar");
+			return $dt;
+		} else {
+			$total = get_data_row($query);
+			return $total->total;
 		}
 	}
 	
@@ -945,21 +1055,21 @@
 	function delete_entity($guid)
 	{
 		global $CONFIG;
-		

-		// TODO Make sure this deletes all metadata/annotations/relationships/etc!!

+		
+		// TODO Make sure this deletes all metadata/annotations/relationships/etc!!
 		
 		$guid = (int)$guid;
-		if ($entity = get_entity($guid)) {

-			if (trigger_event('delete',$entity->type,$entity)) {

-				if ($entity->canEdit()) {

-					$entity->clearMetadata();

-					$entity->clearAnnotations();

+		if ($entity = get_entity($guid)) {
+			if (trigger_event('delete',$entity->type,$entity)) {
+				if ($entity->canEdit()) {
+					$entity->clearMetadata();
+					$entity->clearAnnotations();
 					$entity->clearRelationships();
-					$res = delete_data("DELETE from {$CONFIG->dbprefix}entities where guid={$guid}");

-					return $res;

-				} 

-			}

-		}

+					$res = delete_data("DELETE from {$CONFIG->dbprefix}entities where guid={$guid}");
+					return $res;
+				} 
+			}
+		}
 		return false;
 		
 	}
@@ -1075,141 +1185,141 @@
 			}
 		}
 	}
-	

-	/**

-	 * Determines whether or not the specified user can edit the specified entity.

-	 * 

-	 * This is extendible by registering a plugin hook taking in the parameters 'entity' and 'user',

-	 * which are the entity and user entities respectively

-	 * 

-	 * @see register_plugin_hook 

-	 *

-	 * @param int $entity_guid The GUID of the entity

-	 * @param int $user_guid The GUID of the user

-	 * @return true|false Whether the specified user can edit the specified entity.

-	 */

-	function can_edit_entity($entity_guid, $user_guid = 0) {

-		

-		if ($user_guid == 0) {

-			if (isset($_SESSION['user'])) {

-				$user = $_SESSION['user'];

-			} else {

-				$user = null;

-			}

-		} else {

-			$user = get_entity($user_guid);

+	
+	/**
+	 * Determines whether or not the specified user can edit the specified entity.
+	 * 
+	 * This is extendible by registering a plugin hook taking in the parameters 'entity' and 'user',
+	 * which are the entity and user entities respectively
+	 * 
+	 * @see register_plugin_hook 
+	 *
+	 * @param int $entity_guid The GUID of the entity
+	 * @param int $user_guid The GUID of the user
+	 * @return true|false Whether the specified user can edit the specified entity.
+	 */
+	function can_edit_entity($entity_guid, $user_guid = 0) {
+		
+		if ($user_guid == 0) {
+			if (isset($_SESSION['user'])) {
+				$user = $_SESSION['user'];
+			} else {
+				$user = null;
+			}
+		} else {
+			$user = get_entity($user_guid);
+		}
+
+		if (($entity = get_entity($entity_guid)) && (!is_null($user))) {
+
+			if ($entity->getOwner() == $user->getGUID()) return true;
+			if ($entity->type == "user" && $entity->getGUID() == $user->getGUID()) return true;
+			
+			return trigger_plugin_hook('permissions_check',$entity->type,array('entity' => $entity, 'user' => $user),false);
+		
+		} else {
+			
+			return false;
+			
 		}
-

-		if (($entity = get_entity($entity_guid)) && (!is_null($user))) {

-

-			if ($entity->getOwner() == $user->getGUID()) return true;

-			if ($entity->type == "user" && $entity->getGUID() == $user->getGUID()) return true;

-			

-			return trigger_plugin_hook('permissions_check',$entity->type,array('entity' => $entity, 'user' => $user),false);

-		

-		} else {

-			

-			return false;

-			

-		}

-		

-	}

-	

-	/**

-	 * Gets the URL for an entity, given a particular GUID

-	 *

-	 * @param int $entity_guid The GUID of the entity

-	 * @return string The URL of the entity

-	 */

-	function get_entity_url($entity_guid) {

-		

-		global $CONFIG;

-		if ($entity = get_entity($entity_guid)) {

-

-			$url = "";

-			

-			if (isset($CONFIG->entity_url_handler[$entity->getType()][$entity->getSubType()])) {

-				$function =  $CONFIG->entity_url_handler[$entity->getType()][$entity->getSubType()];

-				if (is_callable($function)) {

-					$url = $function($entity);

-				}

-			}

-			if (isset($CONFIG->entity_url_handler[$entity->getType()]['all'])) {

-				$function =  $CONFIG->entity_url_handler[$entity->getType()]['all'];

-				if (is_callable($function)) {

-					$url = $function($entity);

-				}

-			}

-			if (isset($CONFIG->entity_url_handler['all']['all'])) {

-				$function =  $CONFIG->entity_url_handler['all']['all'];

-				if (is_callable($function)) {

-					$url = $function($entity);

-				}

-			}

-

-			if ($url == "") {

-				$url = $CONFIG->url . "pg/view/" . $entity_guid;

-			}

-			return $url;

-			

-		}

-		return false;

-		

-	}

-	

-	/**

-	 * Sets the URL handler for a particular entity type and subtype

-	 *

-	 * @param string $function_name The function to register

-	 * @param string $entity_type The entity type

-	 * @param string $entity_subtype The entity subtype

-	 * @return true|false Depending on success

-	 */

-	function register_entity_url_handler($function_name, $entity_type = "all", $entity_subtype = "all") {

-		global $CONFIG;

-		

-		if (!is_callable($function_name)) return false;

-		

-		if (!isset($CONFIG->entity_url_handler)) {

-			$CONFIG->entity_url_handler = array();

-		}

-		if (!isset($CONFIG->entity_url_handler[$entity_type])) {

-			$CONFIG->entity_url_handler[$entity_type] = array();

-		}

-		$CONFIG->entity_url_handler[$entity_type][$entity_subtype] = $function_name;

-		

-		return true;

-		

-	}

-	

-	/**

-	 * Page handler for generic entities view system

-	 *

-	 * @param array $page Page elements from pain page handler

-	 */

-	function entities_page_handler($page) {

-		if (isset($page[0])) {

-			global $CONFIG;

-			set_input('guid',$page[0]);

-			@include($CONFIG->path . "entities/index.php");

-		}

-	}

-	

-	/**

-	 * Entities init function; establishes the page handler

-	 *

-	 */

-	function entities_init() {

-		register_page_handler('view','entities_page_handler');

-	}

+		
+	}
+	
+	/**
+	 * Gets the URL for an entity, given a particular GUID
+	 *
+	 * @param int $entity_guid The GUID of the entity
+	 * @return string The URL of the entity
+	 */
+	function get_entity_url($entity_guid) {
+		
+		global $CONFIG;
+		if ($entity = get_entity($entity_guid)) {
+
+			$url = "";
+			
+			if (isset($CONFIG->entity_url_handler[$entity->getType()][$entity->getSubType()])) {
+				$function =  $CONFIG->entity_url_handler[$entity->getType()][$entity->getSubType()];
+				if (is_callable($function)) {
+					$url = $function($entity);
+				}
+			}
+			if (isset($CONFIG->entity_url_handler[$entity->getType()]['all'])) {
+				$function =  $CONFIG->entity_url_handler[$entity->getType()]['all'];
+				if (is_callable($function)) {
+					$url = $function($entity);
+				}
+			}
+			if (isset($CONFIG->entity_url_handler['all']['all'])) {
+				$function =  $CONFIG->entity_url_handler['all']['all'];
+				if (is_callable($function)) {
+					$url = $function($entity);
+				}
+			}
+
+			if ($url == "") {
+				$url = $CONFIG->url . "pg/view/" . $entity_guid;
+			}
+			return $url;
+			
+		}
+		return false;
+		
+	}
+	
+	/**
+	 * Sets the URL handler for a particular entity type and subtype
+	 *
+	 * @param string $function_name The function to register
+	 * @param string $entity_type The entity type
+	 * @param string $entity_subtype The entity subtype
+	 * @return true|false Depending on success
+	 */
+	function register_entity_url_handler($function_name, $entity_type = "all", $entity_subtype = "all") {
+		global $CONFIG;
+		
+		if (!is_callable($function_name)) return false;
+		
+		if (!isset($CONFIG->entity_url_handler)) {
+			$CONFIG->entity_url_handler = array();
+		}
+		if (!isset($CONFIG->entity_url_handler[$entity_type])) {
+			$CONFIG->entity_url_handler[$entity_type] = array();
+		}
+		$CONFIG->entity_url_handler[$entity_type][$entity_subtype] = $function_name;
+		
+		return true;
+		
+	}
+	
+	/**
+	 * Page handler for generic entities view system
+	 *
+	 * @param array $page Page elements from pain page handler
+	 */
+	function entities_page_handler($page) {
+		if (isset($page[0])) {
+			global $CONFIG;
+			set_input('guid',$page[0]);
+			@include($CONFIG->path . "entities/index.php");
+		}
+	}
+	
+	/**
+	 * Entities init function; establishes the page handler
+	 *
+	 */
+	function entities_init() {
+		register_page_handler('view','entities_page_handler');
+	}
 	
 	/** Register the import hook */
 	register_plugin_hook("import", "all", "import_entity_plugin_hook", 0);
 	
 	/** Register the hook, ensuring entities are serialised first */
-	register_plugin_hook("export", "all", "export_entity_plugin_hook", 0);

-	

-	/** Register init system event **/

+	register_plugin_hook("export", "all", "export_entity_plugin_hook", 0);
+	
+	/** Register init system event **/
 	register_event_handler('init','system','entities_init');
 	
-?>
\ No newline at end of file
+?>