<?php

/**

 * Zend Framework

 *

 * LICENSE

 *

 * This source file is subject to the new BSD license that is bundled

 * with this package in the file LICENSE.txt.

 * It is also available through the world-wide-web at this URL:

 * http://framework.zend.com/license/new-bsd

 * If you did not receive a copy of the license and are unable to

 * obtain it through the world-wide-web, please send an email

 * to license@zend.com so we can send you a copy immediately.

 *

 * @category   Zend

 * @package    Zend_Db

 * @subpackage Expr

 * @copyright  Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 * @version    $Id$

 */

/**

 * Class for SQL SELECT fragments.

 *

 * This class simply holds a string, so that fragments of SQL statements can be

 * distinguished from identifiers and values that should be implicitly quoted

 * when interpolated into SQL statements.

 *

 * For example, when specifying a primary key value when inserting into a new

 * row, some RDBMS brands may require you to use an expression to generate the

 * new value of a sequence.  If this expression is treated as an identifier,

 * it will be quoted and the expression will not be evaluated.  Another example

 * is that you can use Zend_Db_Expr in the Zend_Db_Select::order() method to

 * order by an expression instead of simply a column name.

 *

 * The way this works is that in each context in which a column name can be

 * specified to methods of Zend_Db classes, if the value is an instance of

 * Zend_Db_Expr instead of a plain string, then the expression is not quoted.

 * If it is a plain string, it is assumed to be a plain column name.

 *

 * @category   Zend

 * @package    Zend_Db

 * @subpackage Expr

 * @copyright  Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)

 * @license    http://framework.zend.com/license/new-bsd     New BSD License

 */

class Zend_Db_Expr

{

    /**

     * Storage for the SQL expression.

     *

     * @var string

     */

    protected $_expression;

    /**

     * Instantiate an expression, which is just a string stored as

     * an instance member variable.

     *

     * @param string $expression The string containing a SQL expression.

     */

    public function __construct($expression)

    {

        $this->_expression = (string) $expression;

    }

    /**

     * @return string The string of the SQL expression stored in this object.

     */

    public function __toString()

    {

        return $this->_expression;

    }

}