设计模式-适配器模式

1. 概念

该设计模式的目的在于将各种截然不同的函数接口封装成统一的API。如在PHP中操作数据有mysql、mysqli、pdo三种，即使使用三种不同的数据库操作，我们可以使用适配器模式将其统一成一样的API，类似场景还有缓存适配器。

<?php
interface IDatabase {
	public function conn($host, $user, $password, $dbname);
	public function query($sql);
	public function close();
}

<?php
class MySQL implements IDatabase {
	
	protected $conn;
	
	public function conn($host, $user, $password, $dbname)
	{
		$conn = mysql_connect($host, $user, $password);
		mysql_select_db($dbname, $conn);
		$this->conn = $conn;
	}
	
	public function query($sql)
	{
		return mysql_query($sql, $this->conn);
	}
	
	public function close()
	{
		mysql_close($this->conn);
	}
}

<?php
class MySQLi implements IDatabase {
	
	protected $conn;
	
	public function conn($host, $user, $password, $dbname)
	{
		$conn = mysqli_connect($host, $user, $passwd, $dbname);
		$this->conn = $conn;
	}
	
	public function query($sql)
	{
		return mysqli_query($sql, $this->conn);
	}
	
	public function close()
	{
		mysqli_close($this->conn);
	}
}