How does PHP implement unlimited classification through the idea of transferring references (simple code)

This article describes how to use the reference transfer method in php to implement unlimited classification. the code is extremely simple and can be used by anyone who needs it, it is mainly implemented by storing the id and path of the upper-level classification.

In my Simpla, I used unlimited classification. I used the reference transfer idea of PHP to implement an infinite classification method, which perfectly demonstrated a classification mode similar to this.

Id pid name
1 0 Sichuan
2 0 Chongqing
3 1 Chengdu
4 1 Mianyang
5 3 high-tech zones

The code is as follows:

/*** Convert an array into an infinite classification-transmit the reference idea * @ param array $ items * @ return array */public static function get_tree ($ orig) {// solve the problem that subscript is not from 1 $ items = array (); foreach ($ orig as $ key => $ value) {$ items [$ value ['id'] = $ value;} // Start Assembly $ tree = array (); foreach ($ items as $ key => $ item) {if ($ item ['pid '] = 0) {// if the value is 0, $ tree [] = & $ items [$ key];} else {if (isset ($ items [$ item ['pid ']) {// if a value exists, it is a second-level classification. $ items [$ item ['pid '] ['child'] [] = & $ items [$ key]; // direct value assignment and change for transferring references} else {// at least three levels of classification // because it is a reference transfer idea, $ tree [] = & $ items [$ key] ;}} return $ tree ;}

The above content is very simple. if there is an error or a better method, we hope we can communicate with each other. Thank you .!