图书类程序设计初始化文件

<!--图书类文件: class_book.php-->
<?php
	class book
	{
		private $id;
		private $name;
		private $price;
		private $author;

		function __construct()	//__construct：构造函数，建立连接
		{
			//$this->name=$name;
			//$this->price=$price;
			//$this->author=$author;
		}
		function __set($property_name,$value)
		{
			return $this->$property_name=$value;
		}
		function __get($property_name)
		{
			if(isset($this->$property_name))
			{
				return $this->$property_name;
			}
			else
			{
				return null;
			}
		}

		function add()			//添加书目
		{
			$db=new database();
			$query="INSERT INTO Computer (name,price,author) ";
			$query.="VALUES ('$this->name',$this->price,'$this->author')";
			$db->execute($query);
			$db=null;

		}
		function update()		//修改书目
		{
			$db=new database();
			$query="UPDATE Computer SET ";
			$query.="name='$this->name',price=$this->price,author='$this->author' ";
			$query.="WHERE id=$this->id";
			$db->execute($query);
			$db=null;

		}
		function delete()		//删除书目
		{
			$db=new database();
			$query="DELETE FROM Computer WHERE id=$this->id";
			$db->execute($query);
			$db=null;
		}
		static function query($condition)				//查询书目
		{
			if($condition=="" || $condition==null)
			$condition="";
			else
			$condition="WHERE ".$condition;
			$db=new database();
			$query="SELECT * FROM Computer ".$condition;
			$arr=$db->query($query);
			return $arr;
			$db=null;

		}

	}

/*
	$b=new book("C语言",15.20,"吴强");
	$b->add();
	//$b->__set(new_author,"3");
	//$b->update();
	//$b->delete();
	//*/
?>