<?php
class MySQLDB {
    private $host;                // 主機地址
    private $port;                // 埠號
    private $user;                // 使用者名稱
    private $pwd;                // 密碼
    private $dbname;            // 資料庫名
    private $charset;            // 字符集
    private $link;                // 連線物件
    private
 
 static $instance;
    private function __construct($param){
        $this->initParam($param);
        $this->initConnect();
    }
    private function __clone(){

    }
    // 獲取單例
    public static function getInstance($param= array()){
        if(!self::$instance instanceof self){
            self
 
::$instance= new self($param);
        }
        return self::$instance;
    }
    // 初始化引數
    private function initParam($param){
        $this->host= $param['host']??'127.0.0.1';
        $this->port= $param['port']??'3306';
        $this->user= $param['user']??'';
        $this->pwd= $param
 
['pwd']??'';
        $this->dbname= $param['dbname']??'';
        $this->charset= $param['charset']??'utf8';
    }
    // 連線資料庫
    private function initConnect(){
        $this->link= @mysqli_connect($this->host, $this->user, $this->pwd, $this->dbname, $this->port);
        if(mysqli_connect_error()){
            echo '資料庫連線失敗<br>';
            echo '錯誤資訊：'.mysqli_connect_error(),'<br>';
            echo '錯誤碼：'.mysqli_connect_errno(),'<br>';
            exit;
        }else{
            echo '資料庫連線成功！';
        }
        mysqli_set_charset($this->link, $this->charset);    
    }
    // 資料庫的增刪改查
    private function execute($sql){
        if(!$rs= mysqli_query($this->link, $sql)){
            echo 'SQL語句執行失敗<br>';
            echo '錯誤資訊：'.mysqli_error($this->link),'<br>';
            echo '錯誤碼：'.mysqli_errno($this->link),'<br>';
            echo '錯誤的SQL語句：'.$sql,'<br>';
            exit;
        }
        return $rs;
    }
    // 執行增刪改語句
    public function exec($sql) {
        $key=substr($sql,0,6);
        if(in_array($key,array('insert','update','delete')))
            return $this->execute($sql);
        else{
            echo '非法訪問<br>';
            exit;
        }
    }
    //獲取自動增長的編號
    public function getLastInsertId() {
        return mysqli_insert_id($this->link);
    }
    //執行查詢語句
    private function query($sql) {
        if(substr($sql,0,6)=='select' || substr($sql,0,4)=='show' || substr($sql,0,4)=='desc'){
            return $this->execute($sql);
        }else{
            echo '非法訪問<br>';
            exit;
        }
    }
    //匹配所有資料
    public function fetchAll($sql,$type='assoc') {
        $rs=$this->query($sql);
        $type=$this->getType($type);
        return mysqli_fetch_all($rs,$type);
    }
    //匹配一維陣列
    public function fetchRow($sql,$type='assoc') {
        $list=$this->fetchAll($sql,$type);
        if(!empty($list))
            return $list[0];
        return array();
    }
    //匹配一行一列
    public function fetchColumn($sql) {
        $list=$this->fetchRow($sql,'num');
        if(!empty($list))
            return $list[0];
        return null;
    }
    //獲取匹配型別
    private function getType($type) {
        switch($type){
            case 'num':
                return  MYSQLI_NUM;
            case 'both':
                return  MYSQLI_BOTH;
            default:
                return  MYSQLI_ASSOC;
        }
    }
}

$param= array(
    'user' => 'root',
    'pwd' => '',
    'dbname' => 'sel'
);
$db= MySQLDB::getInstance($param);
// 查詢所有資訊
$listAll= $db->fetchAll('select * from news');
var_dump($listAll);
// 查詢一條記錄
$listRow= $db->fetchRow('select * from news');
var_dump($listRow);
// 查詢一個欄位
$listColumn= $db->fetchColumn('select * from news');
var_dump($listColumn);
?>