PHP develops simple book background system to create login verification code

The verification code function will be used on the login interface.

Here we create a simple verification code file.

The production of a simple verification code is introduced in the "PHP Development User Login Module Production of Simple Verification Code" chapter of our PHP Chinese website "PHP Development Login Registration Tutorial", you can refer to it.

Create a verify.php file to facilitate subsequent calls

Set a 4-digit verification code here

<?php
session_start();
srand((double)microtime()*1000000);
while(($authnum=rand()%10000)<1000);//生成四位随机整数验证码
$_SESSION['auth']=$authnum;

//生成验证码图片
Header("Content-type: image/PNG");
$im = imagecreate(55,18);
$red = ImageColorAllocate($im, 255,0,0);
$white = ImageColorAllocate($im, 200,200,100);
$gray = ImageColorAllocate($im, 250,250,250);
$black = ImageColorAllocate($im, 120,120,50);

imagefill($im,60,20,$gray);

//将四位整数验证码绘入图片
//位置交错
for ($i = 0; $i < strlen($authnum); $i++)
{
   $i%2 == 0?$top = -1:$top = 3;
   imagestring($im, 6, 13*$i+4, 1, substr($authnum,$i,1), $white);
}

for($i=0;$i<100;$i++)   //加入干扰象素
{
   imagesetpixel($im, rand()%70 , rand()%30 , $black);
}

ImagePNG($im);
ImageDestroy($im);
?>