php封装的mysqli类实例有哪些？

<?php
header('content-type:text/html;charset=utf-8');
/*
掌握满足单例模式的必要条件
(1)私有的构造方法-为了防止在类外使用new关键字实例化对象
(2)私有的成员属性-为了防止在类外引入这个存放对象的属性
(3)私有的克隆方法-为了防止在类外通过clone成生另一个对象
(4)公有的静态方法-为了让用户进行实例化对象的操作
*/
class ConnectMysqli{
 //私有的属性
 private static $dbcon=false;
 private $host;
 private $port;
 private $user;
 private $pass;
 private $db;
 private $charset;
 private $link;
 //私有的构造方法
 private function __construct($config=array()){
  $this->host = $config['host'] ? $config['host'] : 'localhost';
  $this->port = $config['port'] ? $config['port'] : '3306';
  $this->user = $config['user'] ? $config['user'] : 'root';
  $this->pass = $config['pass'] ? $config['pass'] : 'root';
  $this->db = $config['db'] ? $config['db'] : 'small2';
  $this->charset=isset($arr['charset']) ? $arr['charset'] : 'utf8';
  //连接数据库
  $this->db_connect();
  //选择数据库
  $this->db_usedb();
  //设置字符集
  $this->db_charset();
  }
  //连接数据库
  private function db_connect(){
  $this->link=mysqli_connect($this->host.':'.$this->port,$this->user,$this->pass);
  if(!$this->link){
   echo "数据库连接失败<br>";
   echo "错误编码".mysqli_errno($this->link)."<br>";
   echo "错误信息".mysqli_error($this->link)."<br>";
   exit;
  }
  }
  //设置字符集
  private function db_charset(){
   mysqli_query($this->link,"set names {$this->charset}");
  }
  //选择数据库
  private function db_usedb(){
   mysqli_query($this->link,"use {$this->db}");
  }
  //私有的克隆
  private function __clone(){
   die('clone is not allowed');
  }
  //公用的静态方法
  public static function getIntance(){
   if(self::$dbcon==false){
   self::$dbcon=new self;
   }
   return self::$dbcon;
  }
  //执行sql语句的方法
  public function query($sql){
   $res=mysqli_query($this->link,$sql);
   if(!$res){
   echo "sql语句执行失败<br>";
   echo "错误编码是".mysqli_errno($this->link)."<br>";
   echo "错误信息是".mysqli_error($this->link)."<br>";
   }
   return $res;
  }
  //打印数据
  public function p($arr){
   echo "<pre>";
   print_r($arr);
   echo "</pre>";
  }
  public function v($arr){
  echo "<pre>";
   var_dump($arr);
   echo "</pre>";
  }
  //获得最后一条记录id
  public function getInsertid(){
   return mysqli_insert_id($this->link);
  }
  /**
  * 查询某个字段
  * @param
  * @return string or int
  */
  public function getOne($sql){
   $query=$this->query($sql);
   return mysqli_free_result($query);
  }
  //获取一行记录,return array 一维数组
  public function getRow($sql,$type="assoc"){
   $query=$this->query($sql);
   if(!in_array($type,array("assoc",'array',"row"))){
    die("mysqli_query error");
   }
   $funcname="mysqli_fetch_".$type;
   return $funcname($query);
  }
  //获取一条记录,前置条件通过资源获取一条记录
  public function getFormSource($query,$type="assoc"){
  if(!in_array($type,array("assoc","array","row")))
  {
   die("mysqli_query error");
  }
  $funcname="mysqli_fetch_".$type;
  return $funcname($query);
  }
  //获取多条数据，二维数组
  public function getAll($sql){
   $query=$this->query($sql);
   $list=array();
   while ($r=$this->getFormSource($query)) {
   $list[]=$r;
   }
   return $list;
  }
   /**
   * 定义添加数据的方法
   * @param string $table 表名
   * @param string orarray $data [数据]
   * @return int 最新添加的id
   */
   public function insert($table,$data){
   //遍历数组，得到每一个字段和字段的值
   $key_str='';
   $v_str='';
   foreach($data as $key=>$v){
   if(empty($v)){
    die("error");
   }
    //$key的值是每一个字段s一个字段所对应的值
    $key_str.=$key.',';
    $v_str.="'$v',";
   }
   $key_str=trim($key_str,',');
   $v_str=trim($v_str,',');
   //判断数据是否为空
   $sql="insert into $table ($key_str) values ($v_str)";
   $this->query($sql);
  //返回上一次增加操做产生ID值
   return $this->getInsertid();
  }
  /*
  * 删除一条数据方法
  * @param1 $table, $where=array('id'=>'1') 表名 条件
  * @return 受影响的行数
  */
  public function deleteOne($table, $where){
   if(is_array($where)){
    foreach ($where as $key => $val) {
     $condition = $key.'='.$val;
    }
   } else {
    $condition = $where;
   }
   $sql = "delete from $table where $condition";
   $this->query($sql);
   //返回受影响的行数
   return mysqli_affected_rows($this->link);
  }
  /*
  * 删除多条数据方法
  * @param1 $table, $where 表名 条件
  * @return 受影响的行数
  */
  public function deleteAll($table, $where){
   if(is_array($where)){
    foreach ($where as $key => $val) {
     if(is_array($val)){
      $condition = $key.' in ('.implode(',', $val) .')';
     } else {
      $condition = $key. '=' .$val;
     }
    }
   } else {
    $condition = $where;
   }
   $sql = "delete from $table where $condition";
   $this->query($sql);
   //返回受影响的行数
   return mysqli_affected_rows($this->link);
  }
  /**
  * [修改操作description]
  * @param [type] $table [表名]
  * @param [type] $data [数据]
  * @param [type] $where [条件]
  * @return [type]
  */
  public function update($table,$data,$where){
   //遍历数组，得到每一个字段和字段的值
   $str='';
  foreach($data as $key=>$v){
   $str.="$key='$v',";
  }
  $str=rtrim($str,',');
  //修改SQL语句
  $sql="update $table set $str where $where";
  $this->query($sql);
  //返回受影响的行数
  return mysqli_affected_rows($this->link);
  }
}
?>

//mysqli测试
$db=ConnectMysqli::getIntance();
//var_dump($db);
/*$sql="select * from acticle";
$list=$db->getAll($sql);
$db->p($list);*/
/*$sql="select * from acticle where acticle_id=95";
$list=$db->getRow($sql);
$db->p($list);
*/
/*$sql="select title from acticle";
$list=$db->getOne($sql);
$db->p($list);不行*/
//$list=$db->insert("users",$_POST);
//$del=$db->deleteOne("users","id=29");
//$del=$db->deleteAll("users","id in(27,28)");
//$up=$db->update("users",$_POST,"id=27");
//print_R($list);