php实现可运算的验证码_php技巧

<?php session_start();  /** * 随机的数字,之和验证码 * 修改日期 2006-12-20 */ function getCode ($length = 32, $mode = 0) { switch ($mode) {    case '1':      $str = '123456789'; <i>1本文来#源gaodai$ma#com搞$代*码*网</i><pre>搞代gaodaima码

break; case ‘2’: $str = ‘abcdefghijklmnopqrstuvwxyz’; break; case ‘3’: $str = ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ’; break; case ‘4’: $str = ‘ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz’; break; case ‘5’: $str = ‘ABCDEFGHIJKLMNPQRSTUVWXYZ123456789’; break; case ‘6’: $str = ‘abcdefghijklmnopqrstuvwxyz1234567890’; break; default: $str = ‘ABCDEFGHIJKLMNPQRSTUVWXYZabcdefghijkmnpqrstuvwxyz23456789’; break; } $result = ”; $l = strlen($str)-1; for($i = 0;$i < $length;$i ++) { $num = rand(0, $l); $result .= $str[$num]; } return $result; } //建立验证图片 function createAuthNumImg($randStr,$imgW=100,$imgH=40,$fontName) { header ("content-type: image/png"); $image = imagecreate($imgW , $imgH); $color_white = imagecolorallocate($image , 255 , 255 , 255); $color_gray = imagecolorallocate($image , 228 , 228 , 228); $color_black = imagecolorallocate($image , 255 , 102 , 204); for ($i = 0 ; $i < 1000 ; $i++) { imagesetpixel($image , mt_rand(0 , $imgW) , mt_rand(0 , $imgH) , $color_gray); } imagerectangle($image , 0 , 0 , $imgW – 1 , $imgH – 1 , $color_gray); for ($i=10;$i<$imgH;$i+=10) imageline($image, 0, $i, $imgW, $i, $color_gray); imagettftext($image,16,5,3,25,$color_black,$fontName,$randStr); for ($i=10;$i