对mysqli函数的理解

注：

1、有时在往数据库插入信息时，会出现乱码，需设置数据库编码：mysqli_set_charset($db, "utf8")

2、mysqli的顺序一般为：

    $return = mysqli_query($db,$sql); //先执行

   $return = mysqli_fetch_assoc( $return);//从结果集中取得一行作为关联数组

return $return; //返回数据

//连接数据库   加 @ 隐藏错误
$db = @mysqli_connect('127.0.0.1','root','123456','php_edu','3306');
if(!$db)
{
    //连接错误，抛出异常
    exit('数据库报错：'.mysqli_connect_error());
}
//设置数据库编码
mysqli_set_charset($db, "utf8");
 
 
//获取当前时间戳
$add_time = time();
$sql_1 = "INSERT INTO `director` (`name`,`phone`,`country`,`add_time`) VALUES ('李安','18855556666','中国','{$add_time }');";
$sql_2 = "UPDATE `director` set name = '黄渤',phone='15566662222' WHERE tid = 4 ;";
$sql_3 = "DELETE FROM `director` WHERE tid = 6;";
$sql_4 = "INSERT INTO `users` (name,phone,country,birthday,weight,height,add_time) VALUES ('周星驰','16655556666','中国','1965-1-20',140,175,'{$add_time }');";
$sql_5 = "SELECT * FROM `users` ORDER BY uid DESC LIMIT 0,5;";
//查询单条数据
$sql_6 = "SELECT * FROM `users` LIMIT 1;";
//查询总条数
$sql_7 = "SELECT COUNT(*) AS count_num FROM `users`;";
 
 //echo '<pre>'.var_export(find($db,$sql_6),true);
 //echo '<pre>'.var_export(find_one($db,'users','name','uid=5'),true);
 // $res = find_one($db,'users','name','uid=5');
 // $return = mysqli_query($db,$sql_7);
  //$return = mysqli_fetch_assoc($return);
 
  //传table值的时候，需要用'' ，不能用反引号了
  $return = count_number($db,'users','country="中国"');
  print_r($return);
 
 
 
 //关闭数据库
 mysqli_close($db);
 
 //统计数量
 function count_number($db,$table,$where)
 {
     $sql = "SELECT COUNT(*) AS count_num FROM ".$table." WHERE ".$where;
     $return = mysqli_query($db,$sql);
     $return = mysqli_fetch_assoc($return);
     return $return['count_num'];
 }
 
 //查询单个数据
  function find_one($db,$table,$field,$where)
  {
      $sql = "SELECT ".$field." FROM ".$table.' WHERE '.$where.' LIMIT 1';
      //针对成功的 SELECT、SHOW、DESCRIBE 或 EXPLAIN 查询，将返回一个 mysqli_result 对象。针对其他成功的查询，将返回 TRUE。如果失败，则返回 FALSE。
      $return = mysqli_query($db,$sql);
      $return = mysqli_fetch_assoc($return);
      return $return;
  }
 
 //查询单条数据
 function find($db,$sql)
 {
     $return = mysqli_query($db,$sql);
     $return = mysqli_fetch_assoc($return);
     return $return;
 }
 
//查询数据库
function select($db,$sql)
{
    //$sql = 'SELECT * FROM '.$table.' WHERE '.$where.' ORDER BY '.$order;;
    //echo $sql;
    $return = mysqli_query($db,$sql);
    if($return)
    {
        //mysqli_fetch_assoc() 函数从结果集中取得一行作为关联数组。
        while($row = mysqli_fetch_assoc($return))
        {
            $rows[] = $row;
        }
        //mysql_free_result() 函数释放结果内存。成功返回true，失败返回false
        mysqli_free_result($return);
    }
    return $rows;
}
 
//插入数据
function insert($db,$sql)
{
    //执行插入
    $return = mysqli_query($db,$sql);
    if($return)
    {
        $return = mysqli_insert_id($db);
    }
    return $return;
}
 
//修改数据
function save($db,$sql)
{
    $return = mysqli_query($db,$sql);
    return $return;
}
 
//删除数据
 function delete($db,$sql)
 {
     $return = mysqli_query($db,$sql);
     return $return;
 }