Recently we’ve been working on a new project that requires caching of both views and database queries. One of the problems I came across I wanted to Result Cache an query I was using for a pager. This caused a couple of problems, one being I needed to be able to clear the cache by its prefix so we would never have a stale cache. Doctrine has a built in deleteByPrefix call for this, however on a pager how do I get it so that it will use a result cache, but still use different indexes for different pages? The following code would not work:

<?php
$this->createQuery('sc')
           // A couple of complex joins here, etc
            ->where('sc.video_id = ?',$id)
            ->orderBy('sc.created_at DESC')
            ->useResultCache(true,sfConfig::get('app_comment_cache'),'comment_index');

Well here the problem is everything is being cached as as the ‘comment_index’ cache, so if you passed that query to a pager, and told it to be on the second page, it’d see the ‘comment_index’ cache exists, and use that. A simple way around this is:

  // Query build...
 ->useResultCache(true,sfConfig::get('app_comment_cache'),'comment_index_'.$page);

In this example page is the parameter you are passing the query and the Doctrine pager to tell it what page cache to look at.

Then a very weird problem was occurring, I was getting more queries if I USED the cache than if I didn’t. Very weird. It seemed that one of the joins object did not seem to be getting stored in the cache. The join looked something like this:

<?php
  $this->createQuery('sc')
         ->leftJoin('sc.User u')
         ->leftJoin('u.Profile p')
         //.... more joins etc

The problem was the profile object was not getting stored in the result cache and thus causing a query each time it was called from the user object. After much hunting around, a long time in #doctrine, and a few leads from a couple of people, it turns out, by default, Doctrine will only serialize the immediate relation to the main object (in this case ‘sc’). However, you can make it so that it will serialize objects further down the line by overriding the function serializeReferences to return true in the class you want to serialize references from. In my example this is the User class. Since our application will never only need the ‘User’ class to be serialized on a result cache I completely overrode the function and made it always return true

<?php
class User extends BaseUser {
  public function serializeReferences($bool=null)
  {
    return true;
  }
}

Of course you can set this on a per object instance via $user->serializeReferences(true). Overriding the method the way I did you need to be careful as you could potentially waste a ton of storage space in your result cache.

Hope this saves someone some head banging and confusion on how using a cache could actually cause more queries if not stored properly.

Recently for a project we had the following situation: Users have their own specific databases, however each database has the same schema. Since there are an unlimited number of databases this prevented us from using databases.yml to define which tables need to go to which databases. The user’s database connection would be defined at run time and we needed only certain tables to be bound to that connection. A bunch of googling turned not much up, mostly talking about defining it in the databases.yml file. After a little bit of searching through some of the Doctrine documentation I came across bindComponent. This allows you to tell a model to use a specific connection. For example:

<?php

$newConn = Doctrine_Manager::connection('mysql://myuser:mypassword@somehost/somedatabase','UsersConnection');
$manager=Doctrine_Manager::getInstance();
$manager->bindComponent('SomeModel','UsersConnection');

The above would bind the model ‘SomeModel’ to the connection ‘UsersConnection’. To make this so that it is automatically done each time it is executed a good place to add it is a custom filter.

Also if you plan on storing the user’s database passwords it is a good practice to encrypt them. Look into possibly using the class sfCrypt for this.

Recently for a client we had a very peculiar problem: a nightly script which checked if a person has done a certain action that day was always flagging everyone. We tested the script multiple times on our servers and it always worked fine. The query had something similar to this:

SELECT * FROM action_table WHERE DATE(action_table.time)=DATE(NOW())

Well after a while of trouble shooting we found out that the system clock on the clients server was skewed and in the wrong time zone. We synced the machines clock and update its time zone. Before it had been in UTC time and we switched it over to EST. What is interesting is that MySQL did not respect the new time zone of the clock, it was still reporting as if the system was set to UTC. We then did a soft restart(reload) on the MySQL service, but it still maintained that it was in a UTC timezone and not EST. It took a hard restart of the MySQL service to have it respect the EST timezone.

All in all, as far as we can tell you need to restart the MySQL service to have it respect a new timezone.

Recently I received an email from Davert.  He noted that the sfSCMIgnoresTaksPlugin would not work on Windows as Windows has a different directory separator.  He sent over a patch which uses PHP’s DIRECTORY_SEPARATOR instead of the coded “/”.  This makes the plugin compatible on Windows.  Thanks Davert.  You can read more about the plugin and download the most recent release at http://www.symfony-project.org/plugins/sfSCMIgnoresTaskPlugin">http://www.symfony-project.org/plugins/sfSCMIgnoresTaskPlugin.

For a client we’ve been working with recently it came to our attention that they needed more frontend servers to keep up with the traffic for their surveys. They use LimeSurvey which is powerful open source survey platform. We set the client up in the cloud to scale as necessary with a load balancer in front. This is when we noticed the problem that LimeSurvey doesn’t work well when a user is bouncing between different frontend servers. LimeSurvey keeps all the user’s session attributes on the local server and not in the database. After googling around for a while, we found other people also had this problem before, and no one had really solved it. We figured we would.

We didn’t feel like doing a ton of extra work to reinvent the wheel in terms of storing the session in the database. We snagged most of the code straight from the Symfony “storage” module which handles it’s session management if you want to store the user sessions in a database. After a quick few modifications, we got it up:

<?php
/**
 * Taken from parts the Symfony package "storage" module
 * @author Ashish Datta ashish@setfive.com
 * @author Matt Daum matt@setfive.com
 * Setfive Consulting, LLC                                                     
 */                                                     

class setfiveSession {
                      
  private $options = array();
  private $sessionIdRegenerated;
                                
  public function initialize()  
  {                             
    $this->options =  array('db_table' => 'session',
                            'db_id_col'   => 'sess_id',
                            'db_data_col' => 'sess_data',
                            'db_time_col' => 'sess_time');
                                                          
    session_set_save_handler(array($this, 'sessionOpen'), 
                             array($this, 'sessionClose'),
                             array($this, 'sessionRead'), 
                             array($this, 'sessionWrite'),
                             array($this, 'sessionDestroy'),
                             array($this, 'sessionGC'));    
                                                            
    // start our session                                    
    // session_start();                                     
  }                                                         
                                                            
  /**                                                       
   * Closes a session.                                      
   *                                                        
   * @return boolean true, if the session was closed, otherwise false
   */                                                                
  public function sessionClose()                                     
  {                                                                  
    // do nothing                                                    
    return true;                                                     
  }                                                                  
                                                                     
  /**                                                                
   * Opens a session.                                                
   *                                                                 
   * @param  string $path  (ignored)                                 
   * @param  string $name  (ignored)                                 
   *                                                                 
   * @return boolean true, if the session was opened, otherwise an exception is thrown
   *                                                                                  
   * @throws <b>Exception</b> If a connection with the database does not exist or cannot be created
   */                                                                                              
  public function sessionOpen($path = null, $name = null)                                          
  {                                                                                                
    // we're assuming LimeSurvey all ready has db settings and opened a db connection              
    return true;                                                                                   
  }                                                                                                
                                                                                                   
                                                                                                   
  /**                                                                                              
   * Destroys a session.                                                                           
   *                                                                                               
   * @param  string $id  A session ID                                                              
   *                                                                                               
   * @return bool true, if the session was destroyed, otherwise an exception is thrown             
   *                                                                                               
   * @throws <b>Exception</b> If the session cannot be destroyed.                                  
   */                                                                                              
  public function sessionDestroy($id)                                                              
  {                                                                                                
    // get table/column                                                                            
    $db_table  = $this->options['db_table'];                                                       
    $db_id_col = $this->options['db_id_col'];                                                      

    // cleanup the session id, just in case
    $id = $this->db_escape($id);           

    // delete the record associated with this id
    $sql = "DELETE FROM $db_table WHERE $db_id_col = '$id'";

    if ($this->db_query($sql))
    {                         
      return true;            
    }                         

    // failed to destroy session
    throw new Exception(sprintf('%s cannot destroy session id "%s" (%s).', get_class($this), $id, mysql_error()));
  }                                                                                                               
                                                                                                                  
                                                                                                                  
  /**                                                                                                             
   * Cleans up old sessions.                                                                                      
   *                                                                                                              
   * @param  int $lifetime  The lifetime of a session                                                             
   *                                                                                                              
   * @return bool true, if old sessions have been cleaned, otherwise an exception is thrown                       
   *                                                                                                              
   * @throws <b>Exception</b> If any old sessions cannot be cleaned                                               
   */                                                                                                             
  public function sessionGC($lifetime)                                                                            
  {                                                                                                               
    // get table/column                                                                                           
    $db_table    = $this->options['db_table'];                                                                    
    $db_time_col = $this->options['db_time_col'];                                                                 

    // delete the record older than the authorised session life time
    $lifetime = $this->db_escape($lifetime); // We never know...    
    $sql = "DELETE FROM $db_table WHERE $db_time_col + $lifetime < UNIX_TIMESTAMP()";

    if (!$this->db_query($sql))
    {                          
      throw new Exception(sprintf('%s cannot delete old sessions (%s).', get_class($this), mysql_error()));
    }                                                                                                      

    return true;
  }             
                
                
  /**           
   * Reads a session.
   *                 
   * @param  string $id  A session ID
   *                                 
   * @return string      The session data if the session was read or created, otherwise an exception is thrown
   *                                                                                                          
   * @throws <b>Exception</b> If the session cannot be read                                                   
   */                                                                                                         
  public function sessionRead($id)                                                                            
  {                                                                                                           
                                                                                                              
    // get table/column                                                                                       
    $db_table    = $this->options['db_table'];                                                                
    $db_data_col = $this->options['db_data_col'];                                                             
    $db_id_col   = $this->options['db_id_col'];                                                               
    $db_time_col = $this->options['db_time_col'];                                                             

    // cleanup the session id, just in case
    $id = $this->db_escape($id);           

    // delete the record associated with this id
    $sql = "SELECT $db_data_col FROM $db_table WHERE $db_id_col = '$id'";

    $result = $this->db_query($sql);

    if ($result != false && $this->db_num_rows($result) == 1)
    {                                                        
      // found the session                                   
      $data = $this->db_fetch_row($result);                  

      return $data[0];
    }                 
    else              
    {                 
      // session does not exist, create it
      $sql = "INSERT INTO $db_table ($db_id_col, $db_data_col, $db_time_col) VALUES ('$id', '', UNIX_TIMESTAMP())";
      if ($this->db_query($sql))                                                                                   
      {                                                                                                            
        return '';                                                                                                 
      }                                                                                                            

      // can't create record
      throw new Exception(sprintf('%s cannot create new record for id "%s" (%s).', get_class($this), $id, mysql_error()));                                                                                                              
    }                                                                                                               
                                                                                                                    
  }                                                                                                                 

  
  /**
   * Writes session data.
   *                     
   * @param  string $id    A session ID
   * @param  string $data  A serialized chunk of session data
   *                                                         
   * @return bool true, if the session was written, otherwise an exception is thrown
   *                                                                                
   * @throws <b>sfDatabaseException</b> If the session data cannot be written       
   */                                                                               
  public function sessionWrite($id, $data)                                          
  {                                                                                 
    // get table/column                                                             
    $db_table    = $this->options['db_table'];                                      
    $db_data_col = $this->options['db_data_col'];                                   
    $db_id_col   = $this->options['db_id_col'];                                     
    $db_time_col = $this->options['db_time_col'];                                   

    // cleanup the session id and data, just in case
    $id   = $this->db_escape($id);                  
    $data = $this->db_escape($data);                

    // update the record associated with this id
    $sql = "UPDATE $db_table SET $db_data_col='$data', $db_time_col=UNIX_TIMESTAMP() WHERE $db_id_col='$id'";

    if ($this->db_query($sql))
    {                         
      return true;            
    }                         

    // failed to write session data
    throw new Exception(sprintf('%s cannot write session data for id "%s" (%s).', get_class($this), $id, mysql_error()));                                                                                                               
  }                                                                                                                 

/**
   * Regenerates id that represents this storage.
   *                                             
   * @param  boolean $destroy Destroy session when regenerating?
   *                                                            
   * @return boolean True if session regenerated, false if error
   *                                                            
   */                                                           
  public function regenerate($destroy = false)                  
  {                                                             
    if ($this->sessionIdRegenerated)                            
    {                                                           
      return;                                                   
    }                                                           

    $this->sessionIdRegenerated = true;
    $currentId = session_id();         
    $newId = session_id();             
    $this->sessionRead($newId);        

    return $this->sessionWrite($newId, $this->sessionRead($currentId));
  }                                                                    
                                                                       
                                                                       
  /**                                                                  
   * Counts the rows in a query result                                 
   *                                                                   
   * @param  resource $result  Result of a query                       
   * @return int Number of rows                                        
   */                                                                  
  protected function db_num_rows($result)                              
  {                                                                    
    return mysql_num_rows($result);                                    
  }                                                                    

  /**
   * Extracts a row from a query result set
   *                                       
   * @param  resource $result  Result of a query
   * @return array Extracted row as an indexed array
   */
  protected function db_fetch_row($result)
  {
    return mysql_fetch_row($result);
  }

  /**
   * Executes an SQL Query
   *
   * @param  string $query  The query to execute
   * @return mixed The result of the query
   */
  protected function db_query($query)
  {
    return @mysql_query($query);
  }

  /**
   * Escapes a string before using it in a query statement
   *
   * @param  string $string  The string to escape
   * @return string The escaped string
   */
  protected function db_escape($string)
  {
    return mysql_real_escape_string($string);
  }

}

$sfSessionHandler = new setfiveSession();
$sfSessionHandler->initialize();

This requires you create a table in your MySQL database called session. Here is a dump of the create statement for the table:

CREATE TABLE IF NOT EXISTS `session` (
  `id` int(11) NOT NULL auto_increment,
  `sess_id` varchar(255) NOT NULL,
  `sess_data` text NOT NULL,
  `sess_time` datetime NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=1;

Basically this uses PHP’s session_set_handler function to manipulate how the PHP retrieves, updates, and stores the user’s session. The final touches were to include this class where the user sessions are started in LimeSurvey. We found them in the index.php and sessioncontrol.php files. Include our file from above just before the session_start(); in the code in those two files. In admin/scripts/fckeditor.265/editor/filemanager/connectors/php/upload.php include the file before the first include. Lastly we need to update a couple locations where it does session_regenerate_id and replace it with $sfSessionHandler->regenerate(). You can find these edits in the following three files: admin/usercontrol.php on line 128, admin/login_check.php line 65, and index.php at lines 207 and 215. You should be up and running now, let us know if you have any problems.