验证码

 <?php

header("content-type:image/gif");

include 'util.php';

$length = isset($_GET['n']) ? $_GET['n'] : 4;

$w = $length*20;

$h = 25;

$dotnum = 2;

$linenum = 2;

$i =imagecreatetruecolor($w,$h);

$bgc =imagecolorallocate($i,251,251,251);

imagefilledrectangle($i,0,0,$w,$h,$bgc);

//绘制干扰线

for($n=0;$n<$linenum;$n++){

$cc=imagecolorallocate($i,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));

imageline($i,mt_rand(0,$w),mt_rand(0,$h),mt_rand(0,$w),mt_rand(0,$h),$cc);

}

//绘制干扰点

for($n=0;$n<$dotnum;$n++){

$cc=imagecolorallocate($i,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));

$size=mt_rand(2,6);

imagefilledellipse($i,mt_rand(0,$w),mt_rand(0,$h),$size,$size,$cc);

}

$text =getstr($length,true,true);

for($n=0;$n<$length;$n++){

$c = imagecolorallocate($i,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));

imagettftext($i,mt_rand(12,18),mt_rand(-10,10),$n*20,mt_rand(18,22),$c,'b.ttf',substr($text,$n,1));

}

imagegif($i);

imagedestroy($i);

 

 

//util.php

<?php

/**

 * 功能:返回随机字符串 $len 多少个 $num 是否包含数字  $word 是否包含大写字母

 */

function getString($len=4,$num=true,$word=true){

   $str = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

   if(!$num){

  $str = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

   }

   if(!$word){

       $str = 'abcdefghijklmnopqrstuvwxyz';

  if($num){

      $str = '0123456789abcdefghijklmnopqrstuvwxyz';   

  }

   }

   $s = '';

   for($i=0;$i<$len;$i++){

  $s.=$str[mt_rand(0,strlen($str)-1)];

   }

   return $s;

}

function getstr($length=4,$num=true,$word=true){

$n=0123456789;

$w='abcdefghijklmnopqrstuvwxyz';

$ww='ABCDEFGHIJKLMNOPQRSTUVWXYZ';

$temp='';

if($num && $word){

$t=$n.$w.$ww;

}else if($num){

$t=$n.$w;

}else if($word){

$t=$w.$ww;

}else{

$t=$w;

}

for($i=0;$i<$length;$i++){

$temp.=substr($t,mt_rand(0,strlen($t)-1),1);

}

return $temp;

}

//echo getstr(4,true,false);