PHP achieves unlimited classification (no recursion is used)

This article mainly introduces how PHP can implement unlimited classification without recursion. if you are interested, you can refer to the usage of unlimited classification in development. for example: department structure and document category. The difficulty of an unlimited classification lies in "output" and "query", for example

• Output the document category
  List form;
  • Search for articles contained in all categories under Category.

  1. implementation principle
  Several common implementation methods have their own advantages and disadvantages. The data structure of "improved forward traversal tree" is easy to output and query, but it is complicated in terms of mobile classification and general understanding.

  2. Data structure

  <? Php $ list = array ('id' => 1, 'fid' => 0, 'title' => 'China '), array ('id' => 2, 'fid' => 1, 'title' => 'Jiangsu '), array ('id' => 3, 'fid' => 1, 'title' => 'Anhui '), array ('id' => 4, 'fid' => 8, 'title' => 'jiangyin '), array ('id' => 5, 'fid' => 3, 'title' => 'wuhu '), array ('id' => 6, 'fid' => 3, 'title' => 'Hefei '), array ('id' => 7, 'fid' => 3, 'title' => 'bengbu '), array ('id' => 8, 'fid' => 8, 'title' => 'Wuxi ');?>

  Each category is connected by its parent class id (fid) to form a classification tree. It is worth noting that the fid of classification A cannot be the id of its subclass.

  When using this data structure for output, the most common algorithm is "recursion". friends familiar with the PHP language certainly know that PHP is not good at recursion and has a limited number of recursion times (about 100 times, operating system and configuration vary ).

  Since all recursion can be implemented cyclically, this article has compiled a set of functions for "infinite" classification based on the characteristics of PHP language, which is more efficient than recursive implementation.

  3. output ul List format
  Output the above data as the following HTML

     
     
   
      
      
   
  Jiangsu
   
       
   
        
   
  Wuxi
   
         
   
          
   
  Jiangyin
   
   
         
   
   
       
   
   
      
      
   
  Anhui province
   
       
   
        
  Wuhu
   
        
  Hefei
   
        
  Bengbu
   
       
   
     
     

  This HTML structure is very convenient for front-end use (using JavaScript and CSS to construct a foldable tree. The specific implementation procedure is as follows:

     
     
  
      
      <?php echo get_tree_ul($list, 1); ?>
     
     

  4. output option List format
  

   Jiangsu Wuxi Jiangyin Anhui province Wuhu Hefei Bengbu

  The specific implementation procedure is as follows:

  <? Php // get_tree_option () returns an array and adds a "depth" (depth) column to each element. you can directly output $ options = get_tree_option ($ list, 1 ); foreach ($ options as $ op) {echo''. Str_repeat ("", $ op ['demo'] * 4). $ op ['title'].' <;/option> ';}?> <;/Select>5. search for all subclasses of a category<? Php $ children = get_tree_child ($ list, 0); echo implode (',', $ children); // output:,?>6. search for all parent classes of a category<? Php $ children = get_tree_parent ($ list, 4); echo implode (',', $ children); // 8, 2, 10?>7. related functions<? Phpfunction get_tree_child ($ data, $ fid) {$ result = array (); $ fids = array ($ fid); do {$ cids = array (); $ flag = false; foreach ($ fids as $ fid) {for ($ I = count ($ data)-1; $ I >=0; $ I --) {$ node = $ data [$ I]; if ($ node ['fid'] ==$ fid) {array_splice ($ data, $ I, 1 ); $ result [] = $ node ['id']; $ cids [] = $ node ['id']; $ flag = true ;}}} $ fids = $ cids;} while ($ flag = true); return $ result;} function get_t Ree_parent ($ data, $ id) {$ result = array (); $ obj = array (); foreach ($ data as $ node) {$ obj [$ node ['id'] = $ node;} $ value = isset ($ obj [$ id])? $ Obj [$ id]: null; while ($ value) {$ id = null; foreach ($ data as $ node) {if ($ node ['id'] = $ value ['fid']) {$ id = $ node ['id']; $ result [] = $ node ['id']; break ;}} if ($ id = null) {$ result [] = $ value ['fid'];} $ value = isset ($ obj [$ id])? $ Obj [$ id]: null;} unset ($ obj); return $ result;} function get_tree_ul ($ data, $ fid) {$ stack = array ($ fid ); $ child = array (); $ added_left = array (); $ added_right = array (); $ html_left = array (); $ html_right = array (); $ obj = array (); $ loop = 0; foreach ($ data as $ node) {$ pid = $ node ['fid']; if (! Isset ($ child [$ pid]) {$ child [$ pid] = array ();} array_push ($ child [$ pid], $ node ['id']); $ obj [$ node ['id'] = $ node;} while (count ($ stack)> 0) {$ id = $ stack [0]; $ flag = false; $ node = isset ($ obj [$ id])? $ Obj [$ id]: null; if (isset ($ child [$ id]) {$ cids = $ child [$ id]; $ length = count ($ cids); for ($ I = $ length-1; $ I >=0; $ I --) {array_unshift ($ stack, $ cids [$ I]);} $ obj [$ cids [$ length-1] ['islastchild '] = true; $ obj [$ cids [0] ['isfirstchild '] = true; $ flag = true;} if ($ id! = $ Fid & $ node &&! Isset ($ added_left [$ id]) {if (isset ($ node ['isfirstchild ']) & isset ($ node ['islastchild']) {$ html_left [] ='';} Else if (isset ($ node ['isfirstchild']) {$ html_left [] ='';} Else if (isset ($ node ['islastchild']) {$ html_left [] ='';} Else {$ html_left [] ='';} $ Html_left [] = ($ flag = true )? "{$ Node ['title']}":"{$ Node ['title']}"; $ Added_left [$ id] = true;} if ($ id! = $ Fid & $ node &&! Isset ($ added_right [$ id]) {$ html_right [] = ($ flag = true )? '':''; $ Added_right [$ id] = true;} if ($ flag = false) {if ($ node) {$ cids = $ child [$ node ['fid']; for ($ I = count ($ cids)-1; $ I >=0; $ I --) {if ($ cids [$ I] ==$ id) {array_splice ($ child [$ node ['fid'], $ I, 1); break ;}} if (count ($ child [$ node ['fid']) = 0) {$ child [$ node ['fid'] = null ;}} array_push ($ html_left, array_pop ($ html_right); array_shift ($ stack) ;}$ loop ++; if ($ loop> 5000) return $ html_l Eft;} unset ($ child); unset ($ obj); return implode ('', $ html_left);} function get_tree_option ($ data, $ fid) {$ stack = array ($ fid); $ child = array (); $ added = array (); $ options = array (); $ obj = array (); $ loop = 0; $ depth =-1; foreach ($ data as $ node) {$ pid = $ node ['fid']; if (! Isset ($ child [$ pid]) {$ child [$ pid] = array ();} array_push ($ child [$ pid], $ node ['id']); $ obj [$ node ['id'] = $ node;} while (count ($ stack)> 0) {$ id = $ stack [0]; $ flag = false; $ node = isset ($ obj [$ id])? $ Obj [$ id]: null; if (isset ($ child [$ id]) {for ($ I = count ($ child [$ id])-1; $ I> = 0; $ I --) {array_unshift ($ stack, $ child [$ id] [$ I]);} $ flag = true;} if ($ id! = $ Fid & $ node &&! Isset ($ added [$ id]) {$ node ['dest'] = $ depth; $ options [] = $ node; $ added [$ id] = true ;} if ($ flag = true) {$ depth ++;} else {if ($ node) {for ($ I = count ($ child [$ node ['fid'])-1; $ I >=0; $ I --) {if ($ child [$ node ['fid'] [$ I] ==$ id) {array_splice ($ child [$ node ['fid'], $ I, 1); break; }}if (count ($ child [$ node ['fid']) = 0) {$ child [$ node ['fid'] = null; $ depth -- ;}} array_shift ($ stack) ;}$ loo P ++; if ($ loop> 5000) return $ options;} unset ($ child); unset ($ obj); return $ options ;}?>The above section describes how to use php to implement Infinitus classification without recursion. I hope this will be helpful for your learning.