列表亲子树结构

Question

我已经多层次的父子关系，我想列出它们在树上structure.I也象ID字段的表，parent_id.I试图像

$sql = 'SELECT * FROM list WHERE parent_id = 0'; 
$result = mysql_query($sql, $link); 
while ($row = mysql_fetch_array($result)) { 
    echo $row['id'].'<br>'; 
    $child1_sql = "SELECT * FROM list WHERE parent_id = ".$row['id']; 
    $result1 = mysql_query($child1_sql, $link); 
    while ($row1 = mysql_fetch_array($result1)) { 
     $id = my_recursive_function($row1['parent_id'],$link); 
     echo $id; 
    } 
} 

function my_recursive_function($parent_id,$link) { 

    $child2_sql = "SELECT * FROM list WHERE parent_id = ".$parent_id; 
    $result2 = mysql_query($child2_sql, $link); 
    $row_cnt = mysql_num_rows($result2); 

    if($row_cnt > 0) { 
     while ($row = mysql_fetch_array($result2)) { 
      if($row['parent_id'] == 0) { 
       return $row['id']; 
      } else { 
       my_recursive_function($row['parent_id'],$link); 
      } 
     } 
    } 
} 

但给我

Fatal error: Out of memory (allocated 126877696) (tried to allocate 24 bytes) 

Answer 1

你应该优化sql查询，而不是使用php递归。有一个关于一个不错的文章，也许它可以帮助你：

http://web.archive.org/web/20110606032941/http://dev.mysql.com/tech-resources/articles/hierarchical-data.html