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This article mainly introduces "how to use php to achieve CAPTCHA login". In daily operation, I believe that many people have doubts about how to use php to achieve CAPTCHA login. Xiaobian consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the doubts of "how to log in with php". Next, please follow the editor to study!

Php to achieve CAPTCHA login method: 1, create html page to display CAPTCHA; 2, create php file, accept the CAPTCHA information from the front page; 3, create CAPTCHA to generate PHP file.

This article operating environment: windows10 system, php 7, thinkpad T480 computer.

CAPTCHA is very common in our daily life. Using CAPTCHA has many advantages, such as:

To prevent malicious password cracking. For example, in order to obtain user information, some hackers send data to the server by different means to verify the accuracy of guessing user information.

Prevent malicious ticket brushing and forum irrigation. This kind of phenomenon of watering has existed for a long time in the forum, such as posting bar, constantly sending posts. Now Baidu Tieba has made a time limit on the time for users to post, when there are too many posts in a certain period of time, they can not continue to post.

Prevent malicious requests. For example, if the user submits a form information, it causes a waste of server resources and malicious attacks by constantly requesting data information from the background.

Interesting. This is a personal point of view, when we submit the form, such as encounter some interesting CAPTCHA ways, can enhance the user's love of the site.

Get user information. This is not uncommon in the current site. If we register an account of a site, we need to use the mobile verification code to register successfully. After getting the user's phone number, the website will send some marketing messages to the mobile phone number owner.

So how do we implement the CAPTCHA login function? Let's take a look!

Environment configuration:

You only need the GD extension library with PHP installed locally to use it. How to view it, create a PHP file to write in the file, access the file, if you see that the GD library has been installed, you can use it.

Specific code implementation:

1. Let's create a html page to display the CAPTCHA.

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