PHP &MySQL Hvordan man viser kategorier i alle underkategorier fra databasen

Selvfølgelig er det muligt. Denne kode vil gengive en

• hierarkisk træ, uanset antallet af niveauer

  <?php
    //Connect to mysql server
    $cn = mysql_pconnect("server", "username", "password");
    mysql_select_db("database_name");
    $rs = mysql_query("SELECT id, parent_id, category FROM categories", $cn);
    $childrenTree = array(); //Will store an array of children for each parent
    $categoryNames = array(); //Will store category name for each id
    //We fill $childrenTree and  $categoryNames from database
    while($row = mysql_fetch_array($rs)){
       list($id, $parent_id, $category) = $row;     
       $categoryNames[(string)$id] = $category;
       $parent_id = (string)$parent_id;
       if(!array_key_exists($parent_id, $childrenTree)) 
           $childrenTree[$parent_id] = array();
       $childrenTree[$parent_id][] = (string)$id;
    }
  
   //Main recursive function. I'll asume '0' id is the root node
   function renderTree($parent = "0"){
      global $categoryNames;
      global $childrenTree;
      if($parent != "0") echo "<li> ", $categoryNames[$parent], "\n";
      $children = $childrenTree[$parent];
      if(count($children) > 0){ //If node has children
         echo "<ul>\n";
         foreach($children as $child)
            renderTree($child);
         echo "</ul>\n";
      }
      if($parent != "0") echo "</li>\n";
   }
   renderTree();  //This renders the hierarchical tree
  ?>
  

  Den resulterende HTML for dit eksempel vil være:

  <ul>  
    <li> a & w
      <ul>
          <li> c & sometimes y </li>
          <li> d </li>
      </ul>
    </li>
    <li> b & f </li>
  </ul>
  

  Det vil gengives i en browser som denne:

  • a &w
    • c &nogle gange y
    • d
  • b &f

  Jeg gentager, dette virker for alle niveauer af indlejring. Håber dette hjælper.