Implementation code for php to generate 4-digit verification code_php skills

It is very convenient to implement verification code in php. The key point is to master the usage of php gd library and session.

Looking at the examples of PHP generating verification codes on the Internet, it is all done by combining the PHP gd library with the session and using PHP to generate random numbers.

PHP verification code can be divided into many types, including php picture verification code, php random verification code, and php Chinese verification code etc., use different verification codes according to different application scenarios.

Here is a PHP digital verification code for your reference.

4-digit verification code

/*
*Filename:authpage.php
*/ 
session_start(); 
//srand((double)microtime()*1000000); 
$authnum=$_SESSION['authnum']; 
//验证用户输入是否和验证码一致 
if(isset($_POST['authinput'])) 
{ 
if(strcmp($_POST['authinput'],$_SESSION['authnum'])==0) 
echo"验证成功！"; 
else 
echo"验证失败！"; 
} 
  
  
//生成新的四位整数验证码 
  
  
//while(($authnum=rand()%10000)<1000); 
&#63;> 
<formaction=test4.phpmethod=post> 
<table> 
请输入验证码：<inputtype=textname=authinputstyle="width:80px"><br> 
<inputtype=submitname="验证"value="提交验证码"> 
<inputtype=hiddenname=authnumvalue=<&#63;echo$authnum;&#63;>> 
<imgsrc=authimg.php&#63;authnum=<&#63;echo$authnum;&#63;>> 
</table> 
</form> 

authimg.php

<&#63;php 
//生成验证码图片 
Header("Content-type:image/PNG"); 
srand((double)microtime()*1000000);//播下一个生成随机数字的种子，以方便下面随机数生成的使用 
  
session_start();//将随机数存入session中 
$_SESSION['authnum']=""; 
$im=imagecreate(62,20);//制定图片背景大小 
  
$black=ImageColorAllocate($im,0,0,0);//设定三种颜色 
$white=ImageColorAllocate($im,255,255,255); 
$gray=ImageColorAllocate($im,200,200,200); 
  
imagefill($im,0,0,$gray);//采用区域填充法，设定（0,0） 
  
while(($authnum=rand()%100000)<10000); 
//将四位整数验证码绘入图片 
$_SESSION['authnum']=$authnum; 
imagestring($im,5,10,3,$authnum,$black); 
//用col颜色将字符串s画到image所代表的图像的x，y座标处（图像的左上角为0,0）。 
//如果font是1，2，3，4或5，则使用内置字体 
  
for($i=0;$i<200;$i++)//加入干扰象素 
{ 
$randcolor=ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255)); 
imagesetpixel($im,rand()%70,rand()%30,$randcolor); 
} 
ImagePNG($im); 
ImageDestroy($im); 
&#63;>

The above is the implementation code for PHP to generate a 4-digit verification code. I hope it will be helpful to everyone's learning, so that everyone can master the operation of PHP verification code more skillfully.