PHP implements infinite classification tree

How to implement infinite classification tree in php? This article mainly introduces how to simply implement infinite classification tree lists in PHP, and analyzes PHP's techniques of implementing tree lists through arrays with examples. I hope to be helpful.

The example in this article describes how to simply implement an infinite classification tree list in PHP. Share it with everyone for your reference. The details are as follows:

$items = array( 
  1 => array('id' => 1, 'pid' => 0, 'name' => '江西省'), 
  2 => array('id' => 2, 'pid' => 0, 'name' => '黑龙江省'),
  3 => array('id' => 3, 'pid' => 1, 'name' => '南昌市'), 
  4 => array('id' => 4, 'pid' => 2, 'name' => '哈尔滨市'),
  5 => array('id' => 5, 'pid' => 2, 'name' => '鸡西市'), 
  6 => array('id' => 6, 'pid' => 4, 'name' => '香坊区'), 
  7 => array('id' => 7, 'pid' => 4, 'name' => '南岗区'), 
  8 => array('id' => 8, 'pid' => 6, 'name' => '和兴路'), 
  9 => array('id' => 9, 'pid' => 7, 'name' => '西大直街'), 
  10 => array('id' => 10, 'pid' => 8, 'name' => '东北林业大学'),
  11 => array('id' => 11, 'pid' => 9, 'name' => '哈尔滨工业大学'),
  12 => array('id' => 12, 'pid' => 8, 'name' => '哈尔滨师范大学'),
  13 => array('id' => 13, 'pid' => 1, 'name' => '赣州市'), 
  14 => array('id' => 14, 'pid' => 13, 'name' => '赣县'), 
  15 => array('id' => 15, 'pid' => 13, 'name' => '于都县'), 
  16 => array('id' => 16, 'pid' => 14, 'name' => '茅店镇'), 
  17 => array('id' => 17, 'pid' => 14, 'name' => '大田乡'), 
  18 => array('id' => 18, 'pid' => 16, 'name' => '义源村'), 
  19 => array('id' => 19, 'pid' => 16, 'name' => '上坝村'), 
  20 => array('id' => 20, 'pid' => 0, 'name' => '广东省'), 
  21 => array('id' => 21, 'pid' => 20, 'name' => '广州市'),
); 
$t = array(); 
foreach ($items as $id => $item) { 
  if ($item['pid']) { 
    $items[$item['pid']][$item['id']] = &$items[$item['id']];
    $t[] = $id; 
  } 
} 
foreach($t as $u) { 
  unset($items[$u]); 
} 
echo "<pre class="brush:php;toolbar:false">"; 
print_r($items);

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