How to implement secondary linkage menu in php

php method to implement secondary linkage menu: first create HTML files and PHP files; then write front-end code and back-end logic code; then send a request to the background; finally, use JS to present the value on the page That’s it.

The operating environment of this article: windows7 system, PHP7.1 version, DELL G3 computer

PHP ajax implementation example of secondary linkage menu function

How to implement secondary linkage

Working principle

Second-level linkage is relatively common in development A technical point, it mainly uses JS's local refresh technology ajax. Different from the general page global refresh, it will only refresh the places where we need to change the value. Let's first take a look at its workflow.

• Step 1: We will send a request to the background
• Step 2: After the background accepts the request, it will return a value to us
• Step 3 : Use JS to present the value in the page

##HTML code

        
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PHP code

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