[TYPO3-mvc] adding / multiplying / math operation view helper

[Tim Schoch | GSTALTIG]

I made myself a little calc ViewHelper. Maybe it helps you. But as always... provided without warranty

<?php
/*                                                                      *
 *  COPYRIGHT NOTICE                                                    *
 *                                                                      *
 *  (c) 2010 Tim Schoch <tim at gstaltig.ch>                               *
 *           GSTALTIG GMBH                                              *
 *           All rights reserved                                        *
 *                                                                      *
 *  This script is part of the TYPO3 project. The TYPO3 project 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 2 of the License,   *
 *  or (at your option) any later version.                              *
 *                                                                      *
 *  The GNU General Public License can be found at                      *
 *  http://www.gnu.org/copyleft/gpl.html.                               *
 *                                                                      *
 *  This script 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.                        *
 *                                                                      *
 *  This copyright notice MUST APPEAR in all copies of the script!      *
 *                                                                      */



/**
 * calculate strings
 *
 * @author     Tim Schoch
 * @see        http://www.website55.com/php-mysql/2010/04/how-to-calculate-strings-with-php.html
 * @package    Gstbase
 * @version    $Id$
 * @license    GNU Public License, version 2
 *             http://opensource.org/licenses/gpl-license.php
 */
class Tx_Gstbase_ViewHelpers_CalcViewHelper extends Tx_Fluid_Core_ViewHelper_AbstractViewHelper {


  /**
  * calculate with strings
  * eg: "2 + 4 * 6 / 8" will result in 5
  * @param string the operation
  * @return float the calculated result
  */
  public function render( $value = NULL )
  {
    if ( NULL === $value ) {
      $value = $this->renderChildren();
    }
      // trim white spaces
    $mathString = trim( $value );
      // remove any non-numbers chars; exception for math operators and 'x'
    $mathString = preg_replace( '[^0-9\+-\*x\/\(\) ]', '', $mathString );   
      // replace x with *
    $mathString = str_replace( 'x', '*', $mathString );
      // compute 
    $compute = create_function("", "return (" . $mathString . ");" );
    return 0 + $compute();
  }

}
?>