1: <?php
 2: /**
 3:  * Zend Framework
 4:  *
 5:  * LICENSE
 6:  *
 7:  * This source file is subject to the new BSD license that is bundled
 8:  * with this package in the file LICENSE.txt.
 9:  * It is also available through the world-wide-web at this URL:
10:  * http://framework.zend.com/license/new-bsd
11:  * If you did not receive a copy of the license and are unable to
12:  * obtain it through the world-wide-web, please send an email
13:  * to license@zend.com so we can send you a copy immediately.
14:  *
15:  * @category   Zend
16:  * @package    Zend_Db
17:  * @subpackage Expr
18:  * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
19:  * @license    http://framework.zend.com/license/new-bsd     New BSD License
20:  * @version    $Id: Expr.php 20096 2010-01-06 02:05:09Z bkarwin $
21:  */
22: 
23: 
24: /**
25:  * Class for SQL SELECT fragments.
26:  *
27:  * This class simply holds a string, so that fragments of SQL statements can be
28:  * distinguished from identifiers and values that should be implicitly quoted
29:  * when interpolated into SQL statements.
30:  *
31:  * For example, when specifying a primary key value when inserting into a new
32:  * row, some RDBMS brands may require you to use an expression to generate the
33:  * new value of a sequence.  If this expression is treated as an identifier,
34:  * it will be quoted and the expression will not be evaluated.  Another example
35:  * is that you can use Zend_Db_Expr in the Zend_Db_Select::order() method to
36:  * order by an expression instead of simply a column name.
37:  *
38:  * The way this works is that in each context in which a column name can be
39:  * specified to methods of Zend_Db classes, if the value is an instance of
40:  * Zend_Db_Expr instead of a plain string, then the expression is not quoted.
41:  * If it is a plain string, it is assumed to be a plain column name.
42:  *
43:  * @category   Zend
44:  * @package    Zend_Db
45:  * @subpackage Expr
46:  * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
47:  * @license    http://framework.zend.com/license/new-bsd     New BSD License
48:  */
49: class Zend_Db_Expr
50: {
51:     /**
52:      * Storage for the SQL expression.
53:      *
54:      * @var string
55:      */
56:     protected $_expression;
57: 
58:     /**
59:      * Instantiate an expression, which is just a string stored as
60:      * an instance member variable.
61:      *
62:      * @param string $expression The string containing a SQL expression.
63:      */
64:     public function __construct($expression)
65:     {
66:         $this->_expression = (string) $expression;
67:     }
68: 
69:     /**
70:      * @return string The string of the SQL expression stored in this object.
71:      */
72:     public function __toString()
73:     {
74:         return $this->_expression;
75:     }
76: 
77: }
78: