1<?php 2 3// simple and stupid SPAM protection (using little challenges) 4 5const NUMS = ['zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine']; 6 7function plus($a, $b) { 8 return $a + $b; 9} 10 11function gen_plus($a) { 12 return mt_rand(0, 9 - $a); 13} 14 15function minus($a, $b) { 16 return $a - $b; 17} 18 19function gen_minus($a) { 20 return mt_rand(0, $a); 21} 22 23function print_infix($name, $a, $b) { 24 return "$a $name $b"; 25} 26 27function print_prefix($name, $a, $b) { 28 return "$name($a, $b)"; 29} 30 31const CHALLENGES = [ 32 // name, print, generator 33 ['max', 'print_prefix'], 34 ['min', 'print_prefix'], 35 ['minus', 'print_infix', 'gen_minus'], 36 ['plus', 'print_infix', 'gen_plus'], 37]; 38 39// generate a challenge 40function gen_challenge() { 41 $c = CHALLENGES[mt_rand(0, count(CHALLENGES) - 1)]; 42 43 $a = mt_rand(0, 9); 44 $an = NUMS[$a]; 45 $b = isset($c[2]) ? $c[2]($a) : mt_rand(0, 9); 46 $bn = NUMS[$b]; 47 48 return [$c[0], $an, $bn, $c[1]($c[0], $an, $bn)]; 49} 50 51// test an answer for validity 52function test_answer($name, $an, $bn, $answer) { 53 foreach (CHALLENGES as $x) { 54 if ($x[0] === $name) { 55 $c = $x; 56 break; 57 } 58 } 59 60 $a = array_search($an, NUMS, false); 61 $b = array_search($bn, NUMS, false); 62 63 if (empty($c) || $a === false || $b === false) return false; 64 65 return (NUMS[$c[0]($a, $b)] === $answer); 66} 67
