PHP-Methode zum Herstellen einer Verbindung zur MySQL-Datenbank

<?php
//造一个mysqli对象，造连接对象
$db=new MySQLi("localhost","root","12345678","heiheihei");
//括号里面填的是IP地址域名，用户名，密码，数据库的名字
  //准备一条SQL语句
$sql = "select * from student";
//执行SQL语句,如果是查询语句。成功返回结果及对象
$reslut = $db->query($sql);
//判断返回是否有内容,执行成功
if($reslut)
{
//如果成功了，从结果集对象里找到数据；
  $attr = $reslut->fetch_all();
//返回索引数组：$attr = $reslut->fetch_row()
//返回关联数组：tch_assoc();
//返回对象：$attr = $reslut->fetch_object();
//返回既有索引又有关联：$arrt = $reslut->fetch_array();
  var_dump($attr);
?>

//造连接对象
$db = new MySQLi("localhost","root","12345678","heiheihei");
//准备SQL语句
$sql = "insert into cou values('3-111','嘿嘿','803')";
  //执行SQL语句
$r = $db ->query($sql);
if($r)//如果$r是ture
{
  echo "执行成功";
}
else {
  echo "执行失败";
}

<?php
//造连接对象
$db = new MySQLi("localhost","root","12345678","heiheihei");
//准备SQL语句
$sql = "update cou set cname=&#39;哈哈&#39; where tno=&#39;803&#39;";
  //执行SQL语句
$r = $db ->query($sql);
if($r)
{
  echo "执行成功";
}
else {
  echo "执行失败";
}
?>

<?php
//造连接对象
$db = new MySQLi("localhost","root","12345678","heiheihei");
//准备SQL语句
$sql = "delete from cou where tno=&#39;803&#39;";
  //执行SQL语句
$r = $db ->query($sql);
if($r)
{
  echo "执行成功";
}
else {
  echo "执行失败";
}
?>