How to implement php verification code

Verification code is the abbreviation of the fully automatic Turing test that distinguishes computers and humans. It is a public fully automatic program that distinguishes the user as a computer and a human.

The main application scenarios of verification code: before logging in and registering, before posting and replying to information, and when a suspected machine request is made, human/machine verification is performed.

Implementation steps:

(1) Generate base map;

Depends on PHP image processing library GD

(2) Generate verification content;(Recommended learning:PHP programming from entry to proficiency)

To generate random numbers, use the PHP function rand();

(3) Generate verification code image;

(4) Verify verification content

Requires PHP to operate SESSION basics, Save the verification content on the server side; front-end Ajax basics

Code:

Create a new captcha.php file and write the following code. Implement the verification code picture:

      
View the effect as follows: refresh once, the content may change once
      

      
Create a new form.php file and write the following code . Implementation verification:
      
 输出正确'; # code... }else{ echo $_REQUEST['authcode']; echo $_SESSION['authcode']; echo' 输出错误'; } exit(); } ?>      
  
 
验证码图片： " alt="" width="100" style="max-width:90%"> 换一个? 
 
请输入图片中的内容：  
 
  
 
  
      
The implementation results are as follows. Click to change one, and a verification code will be changed.
      

      
#Enter the content in the picture. If it is correct, it will prompt you to enter it correctly. If it is wrong, it will prompt you to input it incorrectly. Modify the style yourself.
      
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