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A relatively stable PHP login system verification code

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Release： 2016-07-25 09:07:13
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  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<=100;$i++){
  29. $pointX = rand(2,$width-2);
  30. $pointY = rand(2,$height-2);
  31. @imagesetpixel($im, $pointX, $pointY, $pointColor);
  32. }
  34. @imagestring($im, 16, 10, 2, $randval, $stringColor);
  35. $ImageFun='Image'.$type;
  36. $ImageFun($im);
  37. @ImageDestroy($im);
  38. $_SESSION['validatecode'] = $randval;
  39. //产生随机字符串
  40. function randStr($len=6,$format='ALL') {
  41. switch($format) {
  42. case 'ALL':
  43. $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'; break;
  44. case 'CHAR':
  45. $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'; break;
  46. case 'NUMBER':
  47. $chars='0123456789'; break;
  48. default :
  49. $chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  50. break;
  51. }
  52. $string="";
  53. while(strlen($string)<$len)
  54. $string.=substr($chars,(mt_rand()%strlen($chars)),1);
  55. return $string;
  56. }
  57. ?>
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一个比较稳定的php登陆系统验证码
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