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   1  <?php
   2  
   3  class MathCaptcha extends SimpleCaptcha {
   4  
   5      /** Validate a captcha response */
   6  	function keyMatch( $answer, $info ) {
   7          return (int)$answer == (int)$info['answer'];
   8      }
   9  
  10  	function addCaptchaAPI( &$resultArr ) {
  11          list( $sum, $answer ) = $this->pickSum();
  12          $index = $this->storeCaptcha( array( 'answer' => $answer ) );
  13          $resultArr['captcha']['type'] = 'math';
  14          $resultArr['captcha']['mime'] = 'text/tex';
  15          $resultArr['captcha']['id'] = $index;
  16          $resultArr['captcha']['question'] = $sum;
  17      }
  18  
  19      /** Produce a nice little form */
  20  	function getForm() {
  21          list( $sum, $answer ) = $this->pickSum();
  22          $index = $this->storeCaptcha( array( 'answer' => $answer ) );
  23  
  24          $form = '<table><tr><td>' . $this->fetchMath( $sum ) . '</td>';
  25          $form .= '<td>' . Html::input( 'wpCaptchaWord', false, false, array( 'tabindex' => '1', 'autocomplete' => 'off', 'required' ) ) . '</td></tr></table>';
  26          $form .= Html::hidden( 'wpCaptchaId', $index );
  27          return $form;
  28      }
  29  
  30      /** Pick a random sum */
  31  	function pickSum() {
  32          $a = mt_rand( 0, 100 );
  33          $b = mt_rand( 0, 10 );
  34          $op = mt_rand( 0, 1 ) ? '+' : '-';
  35          $sum = "{$a} {$op} {$b} = ";
  36          $ans = $op == '+' ? ( $a + $b ) : ( $a - $b );
  37          return array( $sum, $ans );
  38      }
  39  
  40      /** Fetch the math */
  41  	function fetchMath( $sum ) {
  42          if ( class_exists( 'MathRenderer' ) ) {
  43              $math = MathRenderer::getRenderer( $sum, array(), MW_MATH_PNG );
  44          } else {
  45              throw new MWException( 'MathCaptcha requires the Math extension for MediaWiki versions 1.18 and above.' );
  46          }
  47          $html = $math->render();
  48          return preg_replace( '/alt=".*?"/', '', $html );
  49      }
  50  }