<?php /**  * 仿QQ验证码 */ //Session保存路径 $sessSavePath = dirname(__FILE__)."/../data/sessions/"; if(is_writeable($sessSavePath) && is_readable($sessSavePath)){ session_save_path($sessSavePath); } session_start(); //获取随机字符 $rndstring = ''; for($i=0; $i<4; $i++) $rndstring .= chr(mt_rand(65,90)); $img_height=45;    //先定义图片的长、宽 $img_width=10; //如果支持GD，则绘图 if(function_exists("imagecreate")) {  //Firefox部份情况会多次请求的问题，5秒内刷新页面将不改变session  $ntime = time();  if(empty($_SESSION['dd_ckstr_last']) || empty($_SESSION['dd_ckstr']) || ($ntime - $_SESSION['dd_ckstr_last'] > 5))  {   $_SESSION['dd_ckstr'] = strtolower($rndstring);   $_SESSION['dd_ckstr_last'] = $ntime;  }  $rndstring = $_SESSION['dd_ckstr'];  $rndcodelen = strlen($rndstring);  //创建图片，并设置背景色  $im = imagecreate(46,20);  ImageColorAllocate($im, 240,243,248);  //干扰线  $lineColor1 = ImageColorAllocate($im, mt_rand(174,218),mt_rand(190,225),mt_rand(217,237));  for($j=1;$j<=2;$j=$j+3)  {   imageline($im,0,$j+mt_rand(1,15),48,$j+mt_rand(1,15),$lineColor1);  }  //输出文字  $fontColor = ImageColorAllocate($im, mt_rand(0,150),mt_rand(0,150),mt_rand(0,150));  for($i=0;$i<$rndcodelen;$i++)  {   $bc = mt_rand(0,1);   $rndstring[$i] = strtoupper($rndstring[$i]);   imagestring($im,mt_rand(3,5),$i*$img_height/4+mt_rand(1,5),mt_rand(1,$img_width/2), $rndstring[$i], $fontColor);  }  header("Pragma:no-cache"r"n");  header("Cache-Control:no-cache"r"n");  header("Expires:0"r"n");  //输出特定类型的图片格式，优先级为 gif -> jpg ->png  if(function_exists("imagepng"))  {   header("content-type:image/png"r"n");   imagepng($im);  }  else  {   header("content-type:image/jpeg"r"n");   imagejpeg($im);  }  ImageDestroy($im);  exit(); } else {  //不支持GD，只输出字母 ABCD  $_SESSION['dd_ckstr'] = "abcd";  $_SESSION['dd_ckstr_last'] = '';  header("content-type:image/png"r"n");  header("Pragma:no-cache"r"n");  header("Cache-Control:no-cache"r"n");  header("Expires:0"r"n");  $fp = fopen("data/vdcode.jpg","r");  echo fread($fp,filesize("data/vdcode.jpg"));  fclose($fp);  exit(); } ?>