$items = array(
array('id'=>1,'pid'=>0,'name'=>'一級11'),
array('id'=>2,'pid'=>0,'name'=>'一級12'),
array('id'=>3,'pid'=>1,'name'=>'二級21'),
array('id'=>4,'pid'=>3,'name'=>'三級31'),
array('id'=>5,'pid'=>1,'name'=>'二級22'),
array('id'=>6,'pid'=>3,'name'=>'三級32'),
array('id'=>7,'pid'=>6,'name'=>'四級41'),
);
$i = 0;
function formatTree($arr, $pid = 0){
$tree = array();
$temp = array();
global $i;
if($arr){
foreach($arr as $k=>$v){
if($v['pid'] == $pid){//
$temp = formatTree($arr, $v['id']);
$temp && $v['son'] = $temp;
$tree[] = $v;
}
}
}
return $tree;
}
print_r(formatTree($items));

function genTree($items) {
??? $tree = array(); //格式化好的樹
??? foreach ($items as $item)
??????? if (isset($items[$item['pid']])){
??????????? $items[$item['pid']]['son'][] = &$items[$item['id']];
??????? }
??????? else{
??????????? $tree[] = &$items[$item['id']];
??????? }
??? return $tree;
}

PHP編程$items = array(
??? 1 => array('id' => 1, 'pid' => 0, 'name' => '一級11'),
??? 2 => array('id' => 2, 'pid' => 1, 'name' => '二級21'),
??? 3 => array('id' => 3, 'pid' => 1, 'name' => '二級23'),
??? 4 => array('id' => 4, 'pid' => 9, 'name' => '三級31'),
??? 5 => array('id' => 5, 'pid' => 4, 'name' => '四級43'),
??? 6 => array('id' => 6, 'pid' => 9, 'name' => '三級32'),
??? 7 => array('id' => 7, 'pid' => 4, 'name' => '四級41'),
??? 8 => array('id' => 8, 'pid' => 4, 'name' => '四級42'),
??? 9 => array('id' => 9, 'pid' => 1, 'name' => '二級25'),
??? 10 => array('id' => 10, 'pid' => 11, 'name' => '二級22'),
??? 11 => array('id' => 11, 'pid' => 0, 'name' => '一級12'),
??? 12 => array('id' => 12, 'pid' => 11, 'name' => '二級24'),
??? 13 => array('id' => 13, 'pid' => 4, 'name' => '四級44'),
??? 14 => array('id' => 14, 'pid' => 1, 'name' => '二級26'),
??? 15 => array('id' => 15, 'pid' => 8, 'name' => '五級51'),
??? 16 => array('id' => 16, 'pid' => 8, 'name' => '五級52'),
??? 17 => array('id' => 17, 'pid' => 8, 'name' => '五級53'),
??? 18 => array('id' => 18, 'pid' => 16, 'name' => '六級64'),
);
print_r(genTree($items));