Php formula verification code and Chinese character verification code implementation method

In PHP website development, the verification code can effectively protect our forms from malicious submission. However, if you do not use the formula verification code or Chinese character verification code, the verification code can effectively protect our forms from malicious submission. but if you do not use a formula verification code or a Chinese character verification code, simply use a simple letter or digit verification code, is this verification code solution really safe?

We know that simple numbers or letter verification codes can be easily cracked, but computation verification codes or Chinese character verification codes cannot be cracked. Therefore, we recommend that you use verification codes, try to use the formula verification code or Chinese character verification code.

The following are two types of verification code. For more information, see:

1. formula verification code:

2. Chinese character verification code:

Note:

The Chinese character verification code is executed separately. if you obtain the session, the verification code is inconsistent with the session content. However, when the Chinese character verification code file is referenced in the src attribute of the img label, the session is obtained. in this case, the content of the two is consistent.

Interested friends can further improve this.