ADODB, best php database abstraction class

$DB = DB :: getInstance();//get the instance
$DB -> Execute('SELECT * FROM table');
//or you have only one call you can call it directly like this
DB :: getInstance() -> Execute('SELECT * FROM table');

$DB -> update('users',array('user' => 'update_test','name'=>'update_test','surname'=>'update_test','phone' => 4654646),'id=75');

$DB -> update('useri',$_POST,'id=75');

$DB -> insert('users',array('user' => 'insert_test','name'=>'James','surname'=>'Baker','user_level' => 5));
//
$DB -> insert('users',$_POST);
// the same as above, i put the html form input names to match the ones from the database

$DB = DB :: getInstance();
echo $DB -> returnPreparedQuery('SELECT * FROM table WHERE id = ?',5);
//this will output "SELECT * FROM table WHERE id = 5"

$DB = DB :: getInstance();
$DB -> delete('useri','id=75');

/*
   Delegator class for adodb
    Copyright (C) 2007 CodeAssembly.com  

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see http://www.gnu.org/licenses/
*/

/**
 * @package DB
 * @author CodeAssembly
 *
 * Delegator class for adodb
 * USAGE :
 * 
 *
 *  $DB =  db::getInstance();
 *
 *  try
 *  {
 *  	$DB -> insert('tablename',$insert_array);
 * 		$rs = $DB->Execute('select * from users');
 *  }
 *  catch (exception $e)
 *  {
 *  	print_r($e);
 *  }
 *
 *  while ($array = $rs->FetchRow()) {
 *      print_r($array);
 *  }
 *
 *  
 *
*/
define('ADODB_ASSOC_CASE', 2);

class db
{
	function getInstance()
	{
		if (self :: $instance === NULL)
		{
			self :: $instance = new db(); //create class instance
			include('adodb-exceptions.inc.php' ); //include exceptions for php5
			include('adodb.inc.php' );

			self :: $adodb = NewADOConnection(DB_TYPE);
			self :: $adodb -> Connect( DB_SERVER, DB_USERNAME,DB_PASSWORD, DB_NAME ); //connect to database constants are taken from config
			$ADODB_FETCH_MODE = ADODB_FETCH_ASSOC;
		}
		return  self :: $instance;
	}

	/**
	 * Insert the array into table
	 *
	 * @param string $tablename
	 * @param array $record
	 *
	 * Example:
	 * 
	 * $DB -> insert('users',array('user' => 'insert_test','name'=>'James','surname'=>'Baker','user_level' => 5));
	 * $DB -> insert('users',$_POST);
	 * 
	 */
	function insert($tablename,$record)
	{
		
		$rs = self :: $adodb -> Execute( 'SELECT * FROM ' . $tablename . ' LIMIT 1');
		$insert_sql =  self :: $adodb -> GetInsertSQL($rs,$record);
		return self :: $adodb -> Execute( $insert_sql );
	}

	/**
	 * Update table
	 *
	 * @param string $tablename
	 * @param $record $array
	 * @param integer $where
	 * @return result
     *
	 * Example:
	 * 
	 * $DB -> update('useri',array('user' => 'update_test','name'=>'James','surname'=>'Baker','phone' => 04656454),'id=75');
	 * $DB -> update('users',$_POST,'id=75');
	 * 
	 */
	function update($tablename,$record,$where = null,$data = null)
	{
		if ( $where !== Null ) 
		{
			$rs = self :: $adodb -> Execute( 'SELECT * FROM ' . $tablename . ' WHERE ' . $where .' LIMIT 1',$data);
		} else
		{
			$rs = self :: $adodb -> Execute( 'SELECT * FROM ' . $tablename .' LIMIT 1',$data);
		}

		$update_sql = self :: $adodb -> GetUpdateSQL( $rs, $record );
		if ( $update_sql != '')
		{
			return self :: $adodb -> Execute( $update_sql );
		}
		return true;
	}

	/**
	 * Delete record from table
	 *
	 * @param string $tablename
	 * @param string $where
	 * @return result
	 *
	 * Example:
	 * 
	 * $DB -> delete('useri','id=75');
	 * 
	 */
	function delete( $tablename, $where, $params )
	{
		try 
		{
			$result = self :: $adodb -> Execute( 'DELETE FROM '.$tablename.' WHERE '.$where , $params);
		}
		catch ( exception $e )
		{
			if (constant( 'DEBUG' ) === true)
			{
				print_r($e);
			}
		}
		return result;
	}

	/**
	 * Returns a prepared query . Works just like execute , only instead of running the prepared query it returns it
	 *
	 * @param unknown_type $str
	 * @param unknown_type $arr
	 * @return unknown
	 */
	public function returnPreparedQuery ( $str , $arr )
	{
		$temp = explode ( '?' , $str ) ;
		$size = count ($temp) ;
		for ($x=0;$x<$size;$x++)
		{
			if ( ($temp[$x] != '') && ( $arr[$x]) != '' )
			{
				$temp[$x] .=  ' ' .  self ::$instance -> qstr ($arr[$x]) ;
			}			
		}
		return implode ( ' ' , $temp ) ;
	} 

	function __call($method, $args)//call adodb methods
	{
		return call_user_func_array(array(self :: $adodb, $method),$args);
	}

	function __get($property)
	{
		return self :: $adodb -> $property;
	}

	function __set($property, $value)
	{
		self :: $adodb[$property] = $value;
	}

	private function __clone()//do not allow clone
	{
	}

	static private $adodb = false;
	static private $instance = NULL;
}
?>