PHP connects to the database and implements the addition, deletion, modification and query functions of the database

mySQLi database connection: (only applicable to PHP5 and above, please use mySQL to connect after PHP5)

1. Process-oriented method

//连接数据库，参数分别为本地（localhost），用户名（默认是root），密码（默认是空），数据库名（你要连接的数据库名称）。
$link = mysqli_connect('localhost','root','','mydb');
if(mysqli_errno($link)){     //检测数据库是否连接成功，如果连接失败输出错误，否则数据库连接成功
   echo mysqli_error($link);
}else{
   echo '连接数据库成功';
}

2. Object-oriented method

$mysqli = new mysqli('localhost','root','','mydb');
if($mysqli->errno){
          echo   $mysqli->error;
}else{
         echo'连接数据库成功';
}

Add, delete, modify and query the database through the constructor:

1. Add data to the database

function add($sql){
  $mysqli = new mysqli('localhost','root','','mydb');
  mysqli_set_charset($mysqli,'utf8'); //设置编码格式 让数据库支持中文
  if($mysqli->errno){
      echo $mysqli->error;
   }else{
       echo '连接数据库成功';
   }
  $res = $mysqli->query($sql);
   if($res){
       return true;
   }else{
       return false;
   }
}

Example usage: Add data to the table indicated as users

$name = "马云";
$age = 38;
$pwd = 123789;
$sql = "INSERT INTO users (username,age,pwd) VALUES ('$name',$age,$pwd)";
$res = add($sql);
if($res){        //检测是否添加成功
   echo '添加成功';
}else{
   echo '添加失败';
}

2. Update database:

function update($sql){
        $link =mysqli_connect('localhost','root','','mydb');
         mysqli_set_charset($link,'utf8');
        if(mysqli_errno($link)){
                   echo mysqli_error($link);
         }else{
                  echo'连接数据库成功';
        };
        $res =mysqli_query($link,$sql);
        if($res){
                  return true;
        }else{
                 return false;
      }
}

Example usage: add data to the table named users

$sql = "UPDATE users SET username='王健林' WHERE id=23";
$res = update（$sql）;
if($res){
       echo'更新成功';
}else{
       echo'更新失败';
}

3. Delete (use update instead of delete)

function delete($sql){
$link =mysqli_connect('localhost','root','','mydb');
mysqli_set_charset($link,'utf8');
if(mysqli_errno($link)){
       echo mysqli_error($link);
}else{
         echo'连接数据库成功';
};
$res =mysqli_query($link,$sql);
if($res){
      return true;
}else{
      return false;
}
}

Example usage:

$sql  ="DELETE FROM users WHERE id=23";
$res = delete($sql);
if($res){
      echo'删除成功';
}else{
      echo'删除失败';
}

Query:

function getlist($sql){
$link =mysqli_connect('localhost','root','','mydb');
mysqli_set_charset($link,'utf8');
if(mysqli_errno($link)){
      echo mysqli_error($link);
}else{
       echo'连接数据库成功';
};
$res =mysqli_query($link,$sql);
// 返回查询到的所有数据
//    $list = mysqli_fetch_all($res);  //常用
while($list =mysqli_fetch_assoc($res)){
         $arr[] = $list;
}
        return $arr;
}

Example usage:

$sql  ="SELECT * FROM users";
$res = getlist($sql);
print_r($res);