How to achieve infinite level classification through php loop and recursion

php Loops and recursions play an important role in the PHP development process. This article will explain its related knowledge.

php realizes infinite levels of classification through loops and recursions

First use loops to achieve simple level display

//Use PDO to connect to the database

<!--?php
header("content-type:text/html;charset=utf-8");
$pdo = new PDO("mysql:host=127.0.0.1;dbname=ninthexam","root","root");
$rs = $pdo ---> query("select * from city");
while($row = $rs -> fetch()){
    $data[] = $row;
} 
//循环实现分类
foreach($data as $k=>$v)
{
    if($v[&#39;parint_id&#39;] == 0)
    {
        $tmp[] = $v;
        foreach($data as $key=>$value)
        {
            if($v[&#39;city_id&#39;] == $value[&#39;parint_id&#39;])
            {
                $tmp[] = $value;
            }
        }
    }
}
echo "
"; print_r($tmp);

//Use recursion to achieve infinite classification display

//Use recursion Realizing infinite classification

    function digui($data,$parint_id = 0 ,$cengji = 0)
       {
           //使用静态定义
           static $tmp = array();
           foreach($data as $k=>$v)
           {
               //判断如果“层级ID==自增ID”
               if($v['parint_id'] == $parint_id)
               {
                   $v['cengji'] = $cengji;
                   $tmp[] = $v;
                   digui($data,$v['city_id'],$cengji+1);
               }
           }
           return $tmp;
       }
print_r(digui($data,$parint_id = 0 ,$cengji = 0));

The above are several ways to realize simple infinite classification.

This article explains the related operations of PHP loop and recursion to achieve infinite classification. For more related knowledge, please pay attention to the PHP Chinese website.

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