php验证码

PHP写的验证码

Demo.php
 1 function _code($_width = 75,$_height = 25,$_rnd_code = 4,$_flag = false) {        
    
    //创建随机码
    for ($i=0;$i<$_rnd_code;$i++) {
        $_nmsg .= dechex(mt_rand(0,15));
    }
    
    //保存在session
    $_SESSION['code'] = $_nmsg;
    
    //创建一张图像
    $_img = imagecreatetruecolor($_width,$_height);
    
    //白色
    $_white = imagecolorallocate($_img,255,255,255);
    
    //填充
    imagefill($_img,0,0,$_white);
    
    if ($_flag) {
        //黑色,边框
        $_black = imagecolorallocate($_img,0,0,0);
        imagerectangle($_img,0,0,$_width-1,$_height-1,$_black);
    }
    
    //随即画出6个线条
    for ($i=0;$i<6;$i++) {
        $_rnd_color = imagecolorallocate($_img,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));
        imageline($_img,mt_rand(0,$_width),mt_rand(0,$_height),mt_rand(0,$_width),mt_rand(0,$_height),$_rnd_color);
    }
    
    //随即雪花
    for ($i=0;$i<100;$i++) {
        $_rnd_color = imagecolorallocate($_img,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));
        imagestring($_img,1,mt_rand(1,$_width),mt_rand(1,$_height),'*',$_rnd_color);
    }
    
    //输出验证码
    for ($i=0;$i<strlen($_SESSION['code']);$i++) {
        $_rnd_color = imagecolorallocate($_img,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200));
        imagestring($_img,5,$i*$_width/$_rnd_code+mt_rand(1,10),mt_rand(1,$_height/2),$_SESSION['code'][$i],$_rnd_color);
    }
    
    //输出图像
    header('Content-Type: image/png');
    imagepng($_img);
    
    //销毁
    imagedestroy($_img);
}

上面的代码写在Demo.php

　　这是Demo.php将是一个图片，此时想调用验证码

　　只需在Demo1.php中使用:<img  id="code" src="Demo.php" />

如果想点击图片使验证码发生改变:

　　<script type="text/javascript">
 　　　　var code = document.getElementById('code'); 
 　　　　code.onclick = function(){
 　　 　　this.src='code.php?tm='+Math.random();
 　　　　}
　　</script>