1 <?php
 2 /**
 3  * Tools for adding an optional Maths protection question to a form.
 4  * 
 5  * @package cms
 6  * @subpackage comments
 7  */
 8 
 9 class MathSpamProtection {
10 
11     private static $mathProtection = false;
12     
13     /**
14      * Creates the question from random variables, which are also saved to the session.
15      * @return String
16      */
17     static function getMathQuestion(){
18         if(!Session::get("mathQuestionV1")&&!Session::get("mathQuestionV2")){
19             $v1 = rand(1,9);
20             $v2 = rand(1,9);
21             Session::set("mathQuestionV1",$v1);
22             Session::set("mathQuestionV2",$v2);
23         }
24         else{
25             $v1 = Session::get("mathQuestionV1");
26             $v2 = Session::get("mathQuestionV2");
27         }
28         
29         return sprintf(
30             _t('MathSpamProtection.WHATIS',"What is %s plus %s?"), 
31             MathSpamProtection::digitToWord($v1), 
32             MathSpamProtection::digitToWord($v2)
33         );
34     }
35     
36     /**
37      * Checks the given answer if it matches the addition of the saved session variables. Users can answer using words or digits.
38      */
39     static function correctAnswer($answer){
40         $v1 = Session::get("mathQuestionV1");
41         $v2 = Session::get("mathQuestionV2");
42         
43         Session::clear('mathQuestionV1');
44         Session::clear('mathQuestionV2');
45         
46         if(MathSpamProtection::digitToWord($v1 + $v2) == $answer || ($v1 + $v2) == $answer){
47             return true;
48         }
49         return false;
50         
51     }
52     
53     /**
54      * Helper method for converting digits to their equivelant english words
55      */
56     static function digitToWord($num){
57         $numbers = array(_t('MathSpamProtection.ZERO', 'zero'),
58             _t('MathSpamProtection.ONE', 'one'),
59             _t('MathSpamProtection.TWO', 'two'),
60             _t('MathSpamProtection.THREE', 'three'),
61             _t('MathSpamProtection.FOUR', 'four'),
62             _t('MathSpamProtection.FIVE', 'five'),
63             _t('MathSpamProtection.SIX', 'six'),
64             _t('MathSpamProtection.SEVEN', 'seven'),
65             _t('MathSpamProtection.EIGHT', 'eight'),
66             _t('MathSpamProtection.NINE', 'nine'),
67             _t('MathSpamProtection.TEN', 'ten'),
68             _t('MathSpamProtection.ELEVEN', 'eleven'),
69             _t('MathSpamProtection.TWELVE', 'twelve'),
70             _t('MathSpamProtection.THIRTEEN', 'thirteen'),
71             _t('MathSpamProtection.FOURTEEN', 'fourteen'),
72             _t('MathSpamProtection.FIFTEEN', 'fifteen'),
73             _t('MathSpamProtection.SIXTEEN', 'sixteen'),
74             _t('MathSpamProtection.SEVENTEEN', 'seventeen'),
75             _t('MathSpamProtection.EIGHTEEN', 'eighteen'));         
76                                     
77             if($num < 0) return "minus ".($numbers[-1*$num]);
78                         
79         return $numbers[$num];
80     }
81     
82     
83     static function isEnabled() {
84         return self::$mathProtection;
85     }
86     
87     static function setEnabled($math = true) {
88         self::$mathProtection = $math;
89     }
90 
91 }