php数据访问

面向对象的方式
//1.造一个连接对象
$db = new MySQLi("localhost","root","123","mydb");
//2.判断连接是否出错
if(mysqli_connect_error())
{
    echo "连接失败";
    exit(); //退出程序
}

//!mysqli_connect_error() or die("连接失败！");

//3.写SQL语句
//$sql = "select count(*) from Info";
//$sql = "insert into Info values('p001','','','','')";

//4.执行SQL语句,查询语句如果执行成功返回结果集对象，如果执行失败返回false
$result = $db->query($sql);

//!mysqli_connect_error() or die("连接失败！");

//3.写SQL语句
$sql = "select count(*) from Info";
$sql = "insert into Info values('p001','','','','')";

//4.执行SQL语句,查询语句如果执行成功返回结果集对象，如果执行失败返回false
$result = $db->query($sql);



//5.从结果集中读取数据
if($result)
{
    var_dump($result->fetch_row()); //返回一行数据的数组（索引数组）
    while($row = $result->fetch_row())
    {
        var_dump($row);
    }
    
    var_dump($result->fetch_assoc());//返回一行数据（关联数组）
    
    $shuju = $result->fetch_all();//返回所有数据（二维数组）
    
    var_dump($result->fetch_object());//返回一行数据（对象）
    
    echo $shuju[0][0];
    
    
}


//1.造连接对象
$db = new MySQLi("localhost","root","123","mydb");
//2.判断是否出错
!mysqli_connect_error() or die("连接失败！");
//3.写SQL语句
$sql = "select * from Nation";
//4.执行SQL语句
$result = $db->query($sql);
//5.取数据
if($result)
{
    $attr = $result->fetch_all();
    
    echo "<select>";
        
        foreach($attr as $v)
        {
            echo "<option value='{$v[0]}'>{$v[1]}</option>";
        }
        
    echo "</select>";
}