PHP + Mysql + Ajax + JS implement provincial/municipal level 3 linkage _ php instance

Recently, I made a project that requires three levels of interaction between provinces, cities, and cities. after reading a lot of information online, I had the following idea and the basic idea of the code: create the select control option dynamically in JS, ajax is used to obtain the province, city, and district information obtained from the SQL database in PHP. the code is a bit long, but many of them are similar. for example, the method for obtaining JS provinces, municipalities, and districts is similar, different select statements are executed using different parameters in PHP.

Index.html code:

The code is as follows:

Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd>


Provincial/municipal level-3 Linkage