diff --git a/dblayer.php b/dblayer.php
index 4b86e45..1643c27 100644
--- a/dblayer.php
+++ b/dblayer.php
@@ -36,7 +36,7 @@ Optionnaly, you can add the
 require_once ("domframework/verify.php");
 
 /** Permit abstraction on the differents SQL databases available */
-class dblayer extends PDO
+class dblayer
 {
   /** The table name to use */
   public $table = null;
@@ -84,7 +84,8 @@ class dblayer extends PDO
       the table, and re-import the datas (http://www.sqlite.org/omitted.html) */
 
   /** Limit to one instance of the connection to the same database */
-  private static $instance = null;
+  // Based on an idea of http://tonylandis.com/php/php5-pdo-singleton-class/
+  private static $instance = array ();
 
   /** Connection to the database engine
       See http://fr2.php.net/manual/en/pdo.construct.php for the $dsn format
@@ -99,6 +100,7 @@ class dblayer extends PDO
     if (! isset ($driver[0]))
       throw new Exception (_("No valid DSN provided"), 500);
     // Force specifics initialisations
+    $this->dsn = $dsn;
     switch ($driver[0])
     {
     case "sqlite":
@@ -116,56 +118,76 @@ class dblayer extends PDO
           file_exists ($file) &&
           fileowner ($file) === posix_getuid ())
         chmod ($file, 0666);
-      try
+      // Print the instances of PDO objects stored :
+      // var_dump (self::$instance);
+      if (! array_key_exists ($this->dsn, self::$instance))
       {
-        parent::__construct ($dsn, $username, $password, $driver_options);
-        parent::setAttribute (PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
-      }
-      catch (Exception $e)
-      {
-        throw new Exception ("PDO error : ".$e->getMessage(), 500);
+        if ($this->debug)  echo "CONNECT TO DATABASE\n";
+        try
+        {
+          self::$instance[$this->dsn] = new PDO ($dsn, $username, $password,
+                                     $driver_options);
+          self::$instance[$this->dsn]->setAttribute (PDO::ATTR_ERRMODE,
+                                         PDO::ERRMODE_EXCEPTION);
+        }
+        catch (Exception $e)
+        {
+          throw new Exception ("PDO error : ".$e->getMessage(), 500);
+        }
       }
 
       // Force ForeignKeys support (disabled by default)
-      $this->exec("PRAGMA foreign_keys = ON");
+      self::$instance[$this->dsn]->exec ("PRAGMA foreign_keys = ON");
       $this->sep = "`";
       break;
     case "mysql":
-      try
+      if (! array_key_exists ($this->dsn, self::$instance))
       {
-        $driver_options[PDO::MYSQL_ATTR_FOUND_ROWS] = 1;
-        parent::__construct ($dsn, $username, $password, $driver_options);
-        parent::setAttribute (PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
-      }
-      catch (Exception $e)
-      {
-        throw new Exception ("PDO error : ".$e->getMessage(), 500);
+        if ($this->debug)  echo "CONNECT TO DATABASE\n";
+        try
+        {
+          $driver_options[PDO::MYSQL_ATTR_FOUND_ROWS] = 1;
+          self::$instance[$this->dsn] = new PDO ($dsn, $username, $password,
+                                            $driver_options);
+          self::$instance[$this->dsn]->setAttribute (PDO::ATTR_ERRMODE,
+                                                     PDO::ERRMODE_EXCEPTION);
+        }
+        catch (Exception $e)
+        {
+          throw new Exception ("PDO error : ".$e->getMessage(), 500);
+        }
       }
 
       // Set the coding to UTF8
-      $this->exec("SET CHARACTER SET utf8");
+      self::$instance[$this->dsn]->exec ("SET CHARACTER SET utf8");
       $this->sep = "`";
       break;
     case "pgsql":
-      try
+      if (! array_key_exists ($this->dsn, self::$instance))
       {
-        parent::__construct ($dsn, $username, $password, $driver_options);
-        parent::setAttribute (PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
-      }
-      catch (Exception $e)
-      {
-        throw new Exception ("PDO error : ".$e->getMessage(), 500);
+        if ($this->debug)  echo "CONNECT TO DATABASE\n";
+        try
+        {
+          self::$instance[$this->dsn] = new PDO ($dsn, $username, $password,
+                                           $driver_options);
+          self::$instance[$this->dsn]->setAttribute (PDO::ATTR_ERRMODE,
+                                                     PDO::ERRMODE_EXCEPTION);
+        }
+        catch (Exception $e)
+        {
+          throw new Exception ("PDO error : ".$e->getMessage(), 500);
+        }
       }
 
       // Set the coding to UTF8
-      $this->exec("SET NAMES 'utf8'");
+      self::$instance[$this->dsn]->exec ("SET NAMES 'utf8'");
       $this->sep = "\"";
       break;
     default:
       throw new Exception (dgettext("domframework",
                                     "Unknown PDO driver provided"), 500);
     }
-    $this->dsn = $dsn;
+    return self::$instance[$this->dsn];
   }
 
   /** Return the connected database name from DSN used to connect */
@@ -192,11 +214,11 @@ class dblayer extends PDO
     if ($this->sep === "")
       throw new Exception (dgettext("domframework", "Database not connected"),
                            500);
-    switch ($this->getAttribute(PDO::ATTR_DRIVER_NAME))
+    switch (self::$instance[$this->dsn]->getAttribute(PDO::ATTR_DRIVER_NAME))
     {
     case "sqlite":
       $req = "SELECT name FROM sqlite_master WHERE type='table'";
-      $st = $this->prepare ($req);
+      $st = self::$instance[$this->dsn]->prepare ($req);
       $st->execute ();
       $res = array ();
       while ($d = $st->fetch (PDO::FETCH_ASSOC))
@@ -206,7 +228,7 @@ class dblayer extends PDO
       $req = "SELECT TABLE_NAME
               FROM information_schema.tables
               WHERE TABLE_SCHEMA='".$this->databasename()."'";
-      $st = $this->prepare ($req);
+      $st = self::$instance[$this->dsn]->prepare ($req);
       $st->execute ();
       $res = array ();
       while ($d = $st->fetch (PDO::FETCH_ASSOC))
@@ -216,7 +238,7 @@ class dblayer extends PDO
       $req = "SELECT *
               FROM pg_tables
               WHERE schemaname = 'public'";
-      $st = $this->prepare ($req);
+      $st = self::$instance[$this->dsn]->prepare ($req);
       $st->execute ();
       $res = array ();
       while ($d = $st->fetch (PDO::FETCH_ASSOC))
@@ -230,7 +252,7 @@ class dblayer extends PDO
   }
 
   /** Verify if the provided datas can be inserted/updated in the database.
-      @param $datas An array containing the datas to verify with keys 
+      @param $datas An array containing the datas to verify with keys
       @param $updatekey the key to update
       @return an array with the errors in array($key=>array($priority,$message))
     */
@@ -275,7 +297,7 @@ class dblayer extends PDO
         //." ". dgettext("domframework","in")." ".$key);
         continue;
       }
-   
+
       // Check for type inconsistencies if the value is provided
       if (is_null ($datas[$key]))
       {
@@ -286,7 +308,7 @@ class dblayer extends PDO
       {
         $errors[$key] = array ("error", sprintf (
                             dgettext("domframework",
-                  "Errors in consistency : '%s' is not an integer or a string [is %s]"),
+         "Errors in consistency : '%s' is not an integer or a string [is %s]"),
                             $key, gettype ($datas[$key])));
         continue;
       }
@@ -400,12 +422,12 @@ class dblayer extends PDO
       $this->unique = array ($this->primary);
     // TODO : If Unique is not defined nor primary
     // FIXME : If unique is defined, could I test if the primary key is defined
-    // in a parameter of the unique and if it is not add it automatically 
+    // in a parameter of the unique and if it is not add it automatically
     foreach ($this->unique as $k=>$columns)
     {
       if ($this->primary === null)
       {
-        return array (dgettext("domframework", 
+        return array (dgettext("domframework",
                               "No field primary defined for tests in primary"));
       }
 
@@ -491,7 +513,7 @@ class dblayer extends PDO
              "FROM $this->sep$this->tableprefix$table$this->sep ".
              "WHERE $this->sep$column$this->sep=:".md5 ($column);
       if ($this->debug) echo "DEBUG : $req\n";
-      $st = $this->prepare ($req);
+      $st = self::$instance[$this->dsn]->prepare ($req);
       $val = $datas[$foreign];
       $key = $column;
       if ($this->debug) echo "DEBUG BIND : ".$this->fields[$foreign][0]."\n";
@@ -584,7 +606,7 @@ class dblayer extends PDO
     $req .= " VALUES ";
     $req .= "(:".implode (",:", $binds).")";
     if ($this->debug) echo "DEBUG : $req\n";
-    $st = $this->prepare ($req);
+    $st = self::$instance[$this->dsn]->prepare ($req);
     foreach ($datasOK as $key=>$val)
     {
       if ($this->debug) echo "DEBUG BIND : $key(".md5 ($key).")->".
@@ -612,7 +634,7 @@ class dblayer extends PDO
       echo "dblayer execute exception : ".$e->getMessage()."\n";
       exit;
     }
-    $lastID = $this->lastInsertId();
+    $lastID = self::$instance[$this->dsn]->lastInsertId();
     $lastID = $this->hookpostinsert ($datasOK, $lastID);
     return $lastID;
   }
@@ -741,13 +763,13 @@ class dblayer extends PDO
     if ($this->debug) echo "DEBUG : $req\n";
     try
     {
-      $st = $this->prepare ($req);
+      $st = self::$instance[$this->dsn]->prepare ($req);
     }
     catch (Exception $e)
     {
       if ($this->debug) echo "DEBUG : PREPARE ERROR ! Return FALSE".
          $e->getMessage()."\n";
-      throw new Exception ($e->getMessage(), 500);     
+      throw new Exception ($e->getMessage(), 500);
     }
 
     if ($select !== NULL)
@@ -784,7 +806,7 @@ class dblayer extends PDO
       Return the number of rows modified
       @param string|integer $updatekey The key applied on primary key to be
         updated
-      @param array $datas The values to be updated 
+      @param array $datas The values to be updated
       @return the number of lines modified */
   public function update ($updatekey, $datas)
   {
@@ -826,7 +848,7 @@ class dblayer extends PDO
     $req .= " WHERE $this->sep$this->primary$this->sep=:".
               md5 ("PRIMARY".$this->primary);
     if ($this->debug) echo "DEBUG : $req\n";
-    $st = $this->prepare ($req);
+    $st = self::$instance[$this->dsn]->prepare ($req);
     // Add the primary key to field list temporaly. It will permit to update the
     // primary key
     $fields = $this->fields;
@@ -886,7 +908,7 @@ class dblayer extends PDO
     $deletekey = $this->hookpredelete ($deletekey);
     $req = "DELETE FROM $this->sep$this->tableprefix$this->table$this->sep ";
     $req .= "WHERE $this->primary = :primary";
-    $st = $this->prepare ($req);
+    $st = self::$instance[$this->dsn]->prepare ($req);
     if ($this->debug) echo "DEBUG : $req\n";
     if ($this->debug) echo "DEBUG BIND : primary->".
                            var_export ($deletekey, TRUE)."\n";
@@ -926,7 +948,7 @@ class dblayer extends PDO
     $sql = "DROP TABLE $this->sep$this->tableprefix$this->table$this->sep";
     if ($this->debug)
       echo "$sql\n";
-    return $this->exec($sql);
+    return self::$instance[$this->dsn]->exec ($sql);
   }
 
   /** Create the table defined by the differents fields.
@@ -953,7 +975,7 @@ class dblayer extends PDO
                            500);
     if (count ($this->fields) === 0)
       throw new Exception (dgettext("domframework", "No Field defined"), 500);
-    switch ($this->getAttribute(PDO::ATTR_DRIVER_NAME))
+    switch (self::$instance[$this->dsn]->getAttribute(PDO::ATTR_DRIVER_NAME))
     {
     case "sqlite":
       $sql = "CREATE TABLE IF NOT EXISTS ".
@@ -1248,7 +1270,7 @@ class dblayer extends PDO
 
     if ($this->debug)
       echo "$sql\n";
-    return $this->exec($sql);
+    return self::$instance[$this->dsn]->exec ($sql);
   }
 
   /** This function permit to send a SQL request to the database to do a SELECT
@@ -1256,7 +1278,7 @@ class dblayer extends PDO
   public function directRead ($sql)
   {
     if ($this->debug) echo "== Entering directRead\n";
-    $st = $this->prepare ($sql);
+    $st = self::$instance[$this->dsn]->prepare ($sql);
     $st->execute ();
     $res = array ();
     while ($d = $st->fetch (PDO::FETCH_ASSOC))
@@ -1264,9 +1286,40 @@ class dblayer extends PDO
     return $res;
   }
 
+  /** This function disconnect the database. It is normally only used in phpunit
+      unit tests */
+  public function disconnect ()
+  {
+    unset (self::$instance[$this->dsn]);
+  }
+
+  /** The prepare method */
+  public function prepare ($statement, $driver_options = array())
+  {
+    return self::$instance[$this->dsn]->prepare ($statement, $driver_options);
+  }
+
+  /** Start a new Transaction */
+  public function beginTransaction ()
+  {
+    return self::$instance[$this->dsn]->beginTransaction ();
+  }
+
+  /** Commit (validate) a transaction */
+  public function commit ()
+  {
+    return self::$instance[$this->dsn]->commit ();
+  }
+
+  /** RollBack a transaction */
+  public function rollback ()
+  {
+    return self::$instance[$this->dsn]->rollback ();
+  }
+
   /** Hook preinsert
-      This hook is run before inserting a new data in the database, after the 
-      verification 
+      This hook is run before inserting a new data in the database, after the
+      verification
       @param array the data to insert in the database
       @return the modified datas */
   public function hookpreinsert ($data)
@@ -1283,8 +1336,8 @@ class dblayer extends PDO
   }
 
   /** Hook preupdate
-      This hook is run before updating a data in the database, after the 
-      verification 
+      This hook is run before updating a data in the database, after the
+      verification
       @return the modified datas */
   public function hookpreupdate ($updatekey, $data)
   {