PHP面向对象编程实践（在系统类mysqli上再做一层封装）

<?php

class Sql{
    private $host;
    private $port;
    private $user;
    private $pass;
    private $dbname;
    private $charset;

    private $link;
    public $affected_rows;
    public $num_rows;

    public function __construct(array $info =array()){
        $this->host = $info['host'] ?? 'localhost';
        $this->port = $info['port'] ?? 3306;
        $this->user = $info['user'] ?? 'root';
        $this->pass = $info['pass'] ?? 'chz';
        $this->dbname = $info['dbname'] ?? 'demo';
        $this->charset = $info['charset'] ?? 'utf8';
        $this->sql_conn();
        $this->sql_charset();
    }
    //连接数据库
    private function sql_conn(){
        $this->link = @new mysqli($this->host,$this->user,$this->pass,$this->dbname,$this->port);
        if($this->link->connect_error){
            die('Connect Error ('.$this->link->connect_errno.')'.$this->link->connect_error);
        }
    }
    //设置字符集
    private function sql_charset(){
        $sql = "set names {$this->charset}";
        $res = $this->link->query($sql);

        if(!$res){
            die('Charset Error('.$this->link->errno.')'.$this->link->error);
        }
    }
    //数据库写操作
    public function sql_exec($sql){
        $res = $this->link->query($sql);
        if(!$res){
            die('Sql Error('.$this->link->errno.')'.$this->link->error);
        }
        $this->affected_rows = $this->link->affected_rows;
        return $res;
    }
    //获取数据表中的最后一个id
    public function get_sql_last_id(){
        return $this->link->insert_id;
    }
    //数据库查询操作
    public function sql_query($sql,$all = false){
        $res = $this->link->query($sql);
        if(!$res){
            die('Sql Error('.$this->link->errno.')'.$this->link->error);
        }
        if($all){
            return $res->fetch_all(MYSQLI_ASSOC);
        }else{
            return $res->fetch_assoc();
        }
    }

}


$s = new Sql();
$sql = 'select * from students';
$res = $s->sql_query($sql,true);
echo '<pre>';
print_r($res);

//删除最后两条记录
$sql = 'delete from students order by id desc limit 2';
$res = $s->sql_exec($sql,true);
var_dump($res);

//新增两条记录
$sql = "insert into students values(null,'cjk',13)";
$res = $s->sql_exec($sql,true);
$sql = "insert into students values(null,'ghk',12)";
$res = $s->sql_exec($sql,true);

//获取数据表中的最后一个id
echo '<br>'.$s->get_sql_last_id();