PHP连接数据库

$mysql_db = 'jmyp';
$conn = new mysqli('localhost','root','root');
$conn->query('set names utf8');
$conn->select_db($mysql_db);
$sql = "select * from admin";
$row = $conn->query($sql);
$data=array();
echo "start";
while ($tmp=$row->fetch_assoc())
{
    $data[]=$tmp;
}



echo "<pre>";
print_r($data);
echo "</pre>";
echo "end";