php通过什么连接数据库

<?php
$host='127.0.0.1';
$user='root';
$password='root';
$dbName='php';
$link=new mysqli($host,$user,$password,$dbName);
if ($link->connect_error){
 die("连接失败：".$link->connect_error);
}
 $sql="select * from admins";
 $res=$link->query($sql);
 $data=$res->fetch_all();
 var_dump($data);

<?php
$host='127.0.0.1';
$user='root';
$password='root';
$dbName='php';
$pdo=new PDO("mysql:host=$host;dbname=$dbName",$user,$password);
$sql="select * from admins";
$data=$pdo->query($sql)->fetch();
var_dump($data);