MYSQLI连接数据库

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test02";


$conn=new mysqli($servername,$username,$password,$dbname);


if($conn->connect_error){
die('数据库连接失败!'.$conn->connect_error);
}else{
echo "数据库连接成功<br/>";
}


$sql="select * from tb_user";
$result=$conn->query($sql);


if ($result->num_rows > 0) {
   // 输出数据
   while($row = $result->fetch_assoc()) {
       echo $row["id"]. " " . $row["username"]. " " . $row["password"]. "<br/>";
   }
} else {
   echo "0 结果";
}
$conn->close();
?>