php mysqli 增删改查CRUD操作预处理简单封装

对数据库操作做了一个简单的封装，简化调用。本人不太擅长php，学校老师面向对象都没讲解，自己随便封装了一个类，聊以胜无。实在不想在这里吐苦水，但是作为一个大学计算机学科老师连csdn都不知道，对于项目永远是撇开代码只看功能，连面向对象思想都没有，一学期上课整堂课都在讲库函数。观其年事已高，卖弄官腔，倚老卖老的架势，我也是无力怼之~~

对于这学期php的学习，我最大的收获还是自己不务正业时捣鼓着捞了勺渗透的汤喝了喝，真香啊。没想到php会让我在web渗透测试上有了小入门，算是点了个小技能点，不算是真正入门。不过也大致有所了解，也许等这几天忙完手上的事会写上一篇对这段时间web渗透测试学习的总结。

<?php
/**
 * Created by PhpStorm.
 * User: admin
 * Date: 2019-05-17
 * Time: 17:14
 */
class DBHelper
{
    private $host = "localhost";
    private $username = "root";
    private $password = "xxxxxxx";
    private $database = "phpstudy";
    private $connection;

    function __construct()
    {

    }

    private function getConnection()
    {
        return $this->connection;
    }

    private function openConnection(){
        $this->connection = new mysqli($this->host,$this->username,$this->password,$this->database);
    }

    private function closeConnection(){
        $this->connection->close();
    }
	
	// 查找
    public function select($sql,$type_str=null,$params=null){
        $this->openConnection();
        $conn = $this->getConnection();
        if ($type_str!=null || $params!=null) {
            // 构造$stmt->bind_param参数
            $stmt = $conn->prepare($sql);
            $arr = array();
            $arr[] = $type_str;
            for ($i = 0; $i < count($params);$i++) {
                $arr[] = &$params[$i];
            }
            // 回调
            call_user_func_array(array($stmt,'bind_param'), $arr);
            $stmt->execute();
            $meta = $stmt->result_metadata();
            $result_params = array();
            while ($field = $meta->fetch_field()){
                $result_params[] = &$row[$field->name];
            }
            call_user_func_array(array($stmt,'bind_result'),$result_params);
            while($stmt->fetch()){
                foreach ($row as $key=>$val){
                    $c[$key] = $val;
                }
                $result[] = $c;
            }
            $stmt->free_result();
            $this->closeConnection();
            return $result;
        }else{
            $result = $conn->query($sql);
            $rel = array();
            while ($row = $result->fetch_assoc()){
                $rel[] = $row;
            }
            $result->free_result();
            $this->closeConnection();
            return $rel;

        }
    }

	// 增、删、改操作
    public function IUDoption($sql,$type_str=null,$params=null){
        $this->openConnection();
        $conn = $this->getConnection();
        if ($type_str!=null || $params!=null) {
            $stmt = $conn->prepare($sql);
            $arr = array();
            $arr[] = $type_str;
            for ($i = 0; $i < count($params);$i++) {
                $arr[] = &$params[$i];
            }
            call_user_func_array(array($stmt,'bind_param'), $arr);
            $res = $stmt->execute();
            if ($res){
                $stmt->free_result();
                $this->closeConnection();
                return true;
            }else{
                $stmt->free_result();
                $this->closeConnection();
                return false;
            }
        }else{
            $res = $conn->query($sql);
            if ($res){
                $res->free_result();
                $this->closeConnection();
                return true;
            }else{
                $res->free_result();
                $this->closeConnection();
                return false;
            }
        }
    }
}