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doctrine2/lib/Doctrine/Null.php

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<?php
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/*
* $Id$
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* This software consists of voluntary contributions made by many individuals
* and is licensed under the LGPL. For more information, see
* <http://www.phpdoctrine.org>.
*/
#namespace Doctrine::ORM::Internal;
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/**
* Null class representing a null value that has been fetched from
* the database or a fetched, empty association. This is for internal use only.
* User code should never deal with this null object.
*
* Semantics are as follows:
*
* Regular PHP null : Value is undefined. When a field with that value is accessed
* and lazy loading is used the database is queried.
*
* Null object: Null valued of a field or empty association that has already been loaded.
* On access, the database is not queried.
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*
* @package Doctrine
* @subpackage Null
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* @license http://www.opensource.org/licenses/lgpl-license.php LGPL
* @link www.phpdoctrine.org
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* @since 1.0
* @version $Revision$
* @author Konsta Vesterinen <kvesteri@cc.hut.fi>
*/
// static initializer
Doctrine_Null::$INSTANCE = new Doctrine_Null();
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final class Doctrine_Null
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{
public static $INSTANCE;
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public function __construct() {}
public static function getInstance()
{
return self::$INSTANCE;
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}
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public function exists()
{
return false;
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}
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public function __toString()
{
return '';
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}
}