PHP编写登录验证码功能-附调用方法.doc

本文实例为大家分享了一个PHP写的登录验证码功能，供大家参考，具体内容如下
ShowKey.php
<?php
session_start();
//设置COOKIE或Session
functionesetcookie($name,$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($str);
}
//获取随机字符此函数区分字符大小写如果不区分大小写可加入函数strtolower
functiondomake_password($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
functionShowKey(){
 $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=