PHP recursively implements hierarchical tree expansion_php skills

The example in this article shares with you the main code of PHP recursive implementation of hierarchical tree expansion for your reference. The specific content is as follows

Rendering:

Implementation code:

<&#63;php 
  
$db = mysql_connect('localhost', 'root', 'root') or die('Can\'t connect to database'); 
mysql_select_db('test') or die('Can\'t find database : test'); 
$result = mysql_query('select id, fid, name from tree'); 
while($arr = mysql_fetch_array($result)){ 
  $data[] = array( 
    'id' => $arr['id'],  
    'fid' => $arr['fid'], 
    'name' => $arr['name'],  
  ); 
} 
  
// 将数据按照缩进简单排列 见图1 
function data2arr($tree, $rootId = 0, $level = 0) { 
  foreach($tree as $leaf) { 
    if($leaf['fid'] == $rootId) { 
      echo str_repeat('    ', $level) . $leaf['id'] . ' ' . $leaf['name'] . '<br/>'; 
      foreach($tree as $l) { 
        if($l['fid'] == $leaf['id']) { 
          data2arr($tree, $leaf['id'], $level + 1); 
          break; 
        } 
      } 
    } 
  } 
} 
  
data2arr($data); 
echo '<br/>-----------------------------------------------------------------------<br/>'; 
  
// 将数据按照所属关系封装 见图2 
function arr2tree($tree, $rootId = 0) { 
  $return = array(); 
  foreach($tree as $leaf) { 
    if($leaf['fid'] == $rootId) { 
      foreach($tree as $subleaf) { 
        if($subleaf['fid'] == $leaf['id']) { 
          $leaf['children'] = arr2tree($tree, $leaf['id']); 
          break; 
        } 
      } 
      $return[] = $leaf; 
    } 
  } 
  return $return; 
} 
  
$tree = arr2tree($data); 
print_r($tree); 
echo '<br/>-----------------------------------------------------------------------<br/>'; 
  
// 将数据使用HTML再次展现 见图3 
function tree2html($tree) { 
  echo '<ul>'; 
  foreach($tree as $leaf) { 
    echo '<li>' .$leaf['name']; 
    if(! emptyempty($leaf['children'])) tree2html($leaf['children']); 
    echo '</li>'; 
  } 
  echo '</ul>'; 
} 
  
tree2html($tree);

The above is the entire content of this article. I hope it will be helpful to everyone in learning PHP programming.