PHP编写登录验证码功能 附调用方法

//获取随机字符 此函数区分字符大小写 如果不区分大小写可加入函数strtolower
function domake_password($len)
{
$chars = array(
/"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z",/ "0","1","2","3","4","5","6","7","8","9"
);
$charsLen = count($chars) - 1;
shuffle($chars);// 将数组打乱
$output = "";
for ($i=0; $i<$len; $i++)
{
$output .= $chars[mt_rand(0,$charsLen)]; //获得一个数组元素
}
return $output;
}

//显示验证码
function ShowKey(){
$key=domake_password(4);//获取随机值
$set=esetcookie("checkkey",$key);//将随机值写入cookie或session
//是否支持gd库
if(function_exists("imagejpeg"))
{
header ("Content-type: image/jpeg");
$img=imagecreate(47,20);
$blue=imagecolorallocate($img,102,102);
$white=ImageColorAllocate($img,255,255);
$black=ImageColorAllocate($img,71,71);
imagefill($img,$blue);
imagestring($img,5,6,3,$key,$white);
for($i=0;$i<90;$i++) //加入干扰象素
{
imagesetpixel($img,rand()%70,rand()%30,$black);
}
imagejpeg($img);
imagedestroy($img);
}
elseif (function_exists("imagepng"))
{
header ("Content-type: image/png");
$img=imagecreate(47,$black);
}
imagepng($img);
imagedestroy($img);
}
elseif (function_exists("imagegif"))
{
header("Content-type: image/gif");
$img=imagecreate(47,$black);
}
imagegif($img);
imagedestroy($img);
}
elseif (function_exists("imagewbmp"))
{
header ("Content-type: image/vnd.wap.wbmp");
$img=imagecreate(47,$black);
}
imagewbmp($img);
imagedestroy($img);
}
else
{
//不支持验证码
header("content-type:image/jpegrn");
header("Pragma:no-cachern");
header("Cache-Control:no-cachern");
header("Expires:0rn");
$fp = fopen("data/vdcode.jpg","r");
}
}
ShowKey();
?>