一个比较稳定的php登陆系统验证码

2. session_start();
3. $type = 'gif';
4. $width= 56;
5. $height= 22;
6. header("Content-type: image/".$type);
7. srand((double)microtime()*1000000);
8. $randval = randStr(4,"NUMBER");
9. if($type!='gif' && function_exists('imagecreatetruecolor')){
10. $im = @imagecreatetruecolor($width,$height);
11. }else{
12. $im = @imagecreate($width,$height);
13. }
14. $r = Array(225,211,255,223);
15. $g = Array(225,236,237,215);
16. $b = Array(225,236,166,125);
18. $key = rand(0,3);
20. $backColor = ImageColorAllocate($im,$r[$key],$g[$key],$b[$key]);//背景色（随机）
21. $borderColor = ImageColorAllocate($im, 0, 0, 0);//边框色
22. $pointColor = ImageColorAllocate($im, 255, 170, 255);//点颜色
24. @imagefilledrectangle($im, 0, 0, $width - 1, $height - 1, $backColor);//背景位置
25. @imagerectangle($im, 0, 0, $width-1, $height-1, $borderColor); //边框位置
26. $stringColor = ImageColorAllocate($im, 255,51,153);
28. for($i=0;$i$pointX = rand(2,$width-2);
29. $pointY = rand(2,$height-2);
30. @imagesetpixel($im, $pointX, $pointY, $pointColor);
31. }
33. @imagestring($im, 16, 10, 2, $randval, $stringColor);
34. $ImageFun='Image'.$type;
35. $ImageFun($im);
36. @ImageDestroy($im);
37. $_SESSION['validatecode'] = $randval;
38. //产生随机字符串
39. function randStr($len=6,$format='ALL') {
40. switch($format) {
41. case 'ALL':
42. $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'; break;
43. case 'CHAR':
44. $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'; break;
45. case 'NUMBER':
46. $chars='0123456789'; break;
47. default :
48. $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
49. break;
50. }
51. $string="";
52. while(strlen($string)$string.=substr($chars,(mt_rand()%strlen($chars)),1);
53. return $string;
54. }
55. ?>

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