PHP oop 如何以更简单的方式调用另一个类方法？

Question

我是 php OOP 的新手。我有一个关于我的情况的问题。

db.php

class db{

protected $db_host;
protected $db_name;
protected $db_user_name;
protected $db_pass;

public function __construct() {
    $this->db_host="localhost";
    $this->db_name="bs";
    $this->db_user_name="root";
    $this->db_pass="";
}

public function conn(){

    try {   
        $conn = new PDO("mysql:host=$this->db_host;dbname=$this->db_name", $this->db_user_name="root", $this->db_pass);
        $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        return $conn;
    }
    catch(PDOException $e)
        {
        echo $sql . "<br>" . $e->getMessage();
        }
    }
}

item.php

require "../../includes/db.php";

class item{

public $user_uid;
public $last_id;
public $display_item;
public $iid;

protected $item_id;
protected $item_name;
protected $item_price;
protected $item_quantity;

public function add_item($uid,$item_id,$item_n,$item_p,$item_q){

    $db = new db();
    $conn=$db->conn();

    $this->user_uid=$uid;
    $this->item_id=$item_id;
    $this->item_name=$item_n;
    $this->item_price=$item_p;
    $this->item_quantity=$item_q;

    try {
        $sql = "INSERT item(uid,item_id,item_name,item_price,item_quantity) 
                    VALUES('$this->user_uid','$this->item_id','$this->item_name','$this->item_price','$this->item_quantity')";
        $conn->exec($sql);
        $this->last_id=$conn->lastInsertId();
    }

    catch(PDOException $e){
        echo $sql . "<br>" . $e->getMessage();
    }
    $conn = null;
}

public function display_item($uid){

    $db = new db();
    $conn=$db->conn();

    $this->user_uid=$uid;

    try{

        $sql="SELECT * FROM item where uid='$this->user_uid'";
        $statement=$conn->query($sql);

        while($row=$statement->fetch()){

            $this->iid[]=$row['iid'];
            $this->display_item[]=[$row['item_id'],$row['item_name'],$row['item_price'],$row['item_quantity']];

        }

    }
    catch(PDOException $e){
        echo $sql . "<br>" . $e->getMessage();
    }
    $conn = null;
}
}

正如您从 item.php 中看到的，我必须调用

$db = new db();
$conn=$db->conn();

在 add_item() 和 display_item() 中。

所以这意味着我必须访问数据库连接的每个方法，我都必须这样做。有没有更简单的方法通过修改我的代码不在其他类中创建 $db = new db() 来做到这一点？

或

我是否遗漏了一些 PHP 可以做到的功能？

我想要的方式

require "../../includes/db.php";
$db = new db();
$conn=$db->conn();

class item{

...
...

public function add_item($uid,$item_id,$item_n,$item_p,$item_q){
try {
    $sql = "INSERT item(uid,item_id,item_name,item_price,item_quantity) 
                VALUES('$this->user_uid','$this->item_id','$this->item_name','$this->item_price','$this->item_quantity')";
    $conn->exec($sql);
}

public function display_item($uid){

....

try{

        $sql="SELECT * FROM item where uid='$this->user_uid'";
        $statement=$conn->query($sql);

所以我只声明 1 次()

$db = new db();
$conn=$db->conn();

在类 item() 中并将其用于其余方法。

Answer 1

只需在构造函数中添加连接即可。还要添加必要的属性:

class db
{

    protected $db_host;
    protected $db_name;
    protected $db_user_name;
    protected $db_pass;
    protected $db_conn; // add me here

然后在构造函数中，使用那里的凭据进行连接。因此，当您创建对象时，它已经连接，您只需使用属性连接来执行查询和内容:

public function __construct() 
{
    $this->db_host = "localhost";
    $this->db_name = "bs";
    $this->db_user_name = "root";
    $this->db_pass = "";

    // connect
    try {   
        $this->db_conn = new PDO("mysql:host=$this->db_host;dbname=$this->db_name", $this->db_user_name="root", $this->db_pass);
        $this->db_conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $this->db_conn->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
    }
    catch(PDOException $e) {
        echo $sql . "<br>" . $e->getMessage();
        exit;
    }
}

然后，扩展item中的db类。您现在可以在 item 类中使用 db 的 db_conn 属性。

class item extends db
{

    public $user_uid;
    public $last_id;
    public $display_item;
    public $iid;

    protected $item_id;
    protected $item_name;
    protected $item_price;
    protected $item_quantity;


    public function display_item($uid)
    {
        try {

            $stmt = $this->db_conn->prepare('SELECT * FROM item WHERE uid = :uid');
            $stmt->bindValue(':uid', $uid);
            $stmt->execute();

            foreach($stmt->fetchAll(PDO::FETCH_ASSOC) as $row) {
                $this->iid[] = $row['iid'];
                $this->display_item[] = [$row['item_id'], $row['item_name'], $row['item_price'], $row['item_quantity']];
            }

        } catch(PDOException $e) {
            echo $e->getMessage();
            exit;
        }
    }
}

旁注:我在顶部添加了准备好的语句