1. Analysis When we use PHP to make a website, classification is very important. Under the classification, the second classification is called the sub-classification. Now most websites are only classified into the third category: the first classification ( Parent classification)-->Second classification (child classification)-->Third classification (grandchild classification) The more related classifications there are, the more complex and difficult it is to control the program and database. Classification processing and control at the same level It is very simple, because only one database is needed to record this level of classification, such as: system, news and other classifications. The processing at this level is very simple, but for a website, the first-level classification is If it is not enough, it needs to be classified again, such as: system-->linux, windows news-->linux news, windows news. This classification will be clearer, at least people can understand that the system includes linux and windows, and the news includes linux news. and windows news, in order to make the information and materials clearer, we continue to classify: linux-->system tools, kernel, programming languages, development tools... When the classification reaches the third level, the processing of information and materials becomes clearer, that is, It is said that in order to process information clearly, the more detailed the classification, the more convenient it is. This makes it easier to process information and make it easier for netizens to find the information they need with a clear purpose. However, as the classification continues to be refined, the control of programs and databases will become more difficult. It is getting more and more difficult. Difficulty one: How to deal with these related kinship classifications in the database? Difficulty two: How to use PHP to complete this clear relationship? This kind of multi-level and detailed classification is a must for every PHP programmer The problem to be solved is because the classification problem of making a good and excellent website is inevitable, and solving this problem is quite complicated. The biggest problem is the classification processing of the database, because if the database is not handled properly, it will bring huge consequences. The workload even had to re-plan the database... This is not an exaggeration, because many people will use the first-level classification to build a database when dealing with databases. I also adopted this method to handle classification at the time, because most websites They are all classified into the third level, so there are only three classification databases in the database for processing. But when it is necessary to continue to classify downwards, the disadvantages of this approach are revealed, because the further down the classification, the workload and the amount of procedures increase. There will be a huge increase... The method I want to introduce is how to use a classification database to create an infinite downward classification method. Readers who have used Windows know that you can create an unlimited downward classification directory in the Windows folder. Continue to create directories and divide them endlessly. Linux directory creation also has this function. The method I introduced is the same as this form.
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
