PHP编写登录验证码功能 附调用方法

<?php
session_start();
//设置COOKIE或Session
function esetcookie($name,$str,$life=0){
//本函数将字符串 str 全部变小写字符串使验证码输入不区分大小写----在提交表单进行session比较同样需要次函数转化
$_SESSION[$name]=strtolower($str);
}

//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,102,102,102);
$white=ImageColorAllocate($img,255,255,255);
$black=ImageColorAllocate($img,71,71,71);
imagefill($img,0,0,$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(47,20);
$blue=imagecolorallocate($img,102,102,102);
$white=ImageColorAllocate($img,255,255,255);
$black=ImageColorAllocate($img,71,71,71);
imagefill($img,0,0,$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);
}
imagepng($img);
imagedestroy($img);
}
elseif (function_exists("imagegif"))
{
header("Content-type: image/gif");
$img=imagecreate(47,20);
$blue=imagecolorallocate($img,102,102,102);
$white=ImageColorAllocate($img,255,255,255);
$black=ImageColorAllocate($img,71,71,71);
imagefill($img,0,0,$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);
}
imagegif($img);
imagedestroy($img);
}
elseif (function_exists("imagewbmp"))
{
header ("Content-type: image/vnd.wap.wbmp");
$img=imagecreate(47,20);
$blue=imagecolorallocate($img,102,102,102);
$white=ImageColorAllocate($img,255,255,255);
$black=ImageColorAllocate($img,71,71,71);
imagefill($img,0,0,$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);
}
imagewbmp($img);
imagedestroy($img);
}
else
{
//不支持验证码
header("content-type:image/jpeg\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");
}
}
ShowKey();
?>

<img src="ShowKey.php" name="KeyImg" id="KeyImg"  onClick="KeyImg.src='ShowKey.php?'+Math.random()">

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