Example of php verification code (GD library generates verification code)

Let me introduce you to an example of PHP using the GD library to generate verification codes. Friends in need can refer to it.

Generate PNG images through GD, assign the $randval random number to $_SESSION['login_check_num'], and compare it with the $_POST input by the user to determine whether it is correct.

Note: If the server does not enable GD library support, you need to modify the php.ini file so that php supports the GD library. (Topic recommendation: PHP verification code collection)

The code is as follows:

<?php
//调用生成验证码图片
//by http://bbs.it-home.org
if($_GET["action"]=="verifycode")
{
    rand_create();
}
//生成验证码图片
function rand_create()
{
    //通知浏览器将要输出PNG图片
    Header("Content-type: image/PNG");
    //准备好随机数发生器种子 
    srand((double)microtime()*1000000);
    //准备图片的相关参数  
    $im = imagecreate(62,20);
    $black = ImageColorAllocate($im, 0,0,0);  //RGB黑色标识符
    $white = ImageColorAllocate($im, 255,255,255); //RGB白色标识符
    $gray = ImageColorAllocate($im, 200,200,200); //RGB灰色标识符
    //开始作图    
    imagefill($im,0,0,$gray);
    while(($randval=rand()%100000)<10000);{
        $_SESSION["login_check_num"] = $randval;
        //将四位整数验证码绘入图片 
        imagestring($im, 5, 10, 3, $randval, $black);
    }
    //加入干扰象素   
    for($i=0;$i<200;$i++){
        $randcolor = ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255));
        imagesetpixel($im, rand()%70 , rand()%30 , $randcolor);
    }
    //输出验证图片
    ImagePNG($im);
    //销毁图像标识符
    ImageDestroy($im);
}
//检验验证码
function rand_check()
{
    if($_POST["reg_rand"] == $_SESSION["login_check_num"]){
        return true;
    }
    else{
        exit("验证码输入错误");
    }
}
?>