生成树型结构(比如省市区)

<?php
header("Content-type: text/html; charset=utf-8");

function generateTree($items)
{
    $tree = array();
    foreach($items as $item){
        if(isset($items[$item['pid']])){
            $items[$item['pid']]['son'][] = &$items[$item['id']];
        }else{
            $tree[] = &$items[$item['id']];
        }
    }
    return $tree;
}
//需要注意的一点，数组的key值必须与id值保持一致
$items = array(
    1 => array('id' => 1, 'pid' => 0, 'name' => '安徽省'),
    2 => array('id' => 2, 'pid' => 0, 'name' => '浙江省'),
    3 => array('id' => 3, 'pid' => 1, 'name' => '合肥市'),
    4 => array('id' => 4, 'pid' => 3, 'name' => '长丰县'),
    5 => array('id' => 5, 'pid' => 1, 'name' => '安庆市'),
);
echo "<pre>";
print_r(generateTree($items));

上面方法的优化：

<?php
header("Content-type: text/html; charset=utf-8");

function generateTree($items)
{
    foreach($items as $item)
        $items[$item['pid']]['son'][$item['id']] = &$items[$item['id']];
    return isset($items[0]['son']) ? $items[0]['son'] : array();
}

//需要注意的一点，数组的key值必须与id保持一致
$items = array(
    1 => array('id' => 1, 'pid' => 0, 'name' => '安徽省'),
    2 => array('id' => 2, 'pid' => 0, 'name' => '浙江省'),
    3 => array('id' => 3, 'pid' => 1, 'name' => '合肥市'),
    4 => array('id' => 4, 'pid' => 3, 'name' => '长丰县'),
    5 => array('id' => 5, 'pid' => 1, 'name' => '安庆市'),
);
echo "<pre>";
print_r(generateTree($items));

结果：