PHP encapsulated database addition, deletion, modification and query

<?php
	class mysqlSql{//封装函数
		public $db;
		public function __construct($dbname){//构造函数
			$this->db = new PDO("mysql:host=localhost;dbname=".$dbname,&#39;root&#39;,&#39;root&#39;);//数据库连接
		}
		public function zengjia($table,$title,$body){//数据库增加
			$time=time();//当前时间
			$sql = "INSERT INTO ".$table .&#39; (id,title,body,create_time)&#39;." VALUES (null,&#39;$title&#39;,&#39;$body&#39;,$time)";
			$db = $this->db;
			$row = $db->query($sql);
			return $row;

		}
		public function shanchu($table,$id){//数据库删除
			$sql = "DELETE FROM ".$table." WHERE id=".$id; 
			$db = $this->db;
			$row = $db->exec($sql);
			return $row;
		}
		public function gengxin($table,$title,$body,$id){//数据库更新
			$time=time();//当前时间
			$sql = "UPDATE ".$table." SET title=&#39;$title&#39;,body=&#39;$body&#39;,update_time=$time where id=".$id;
			$db =$this->db;
			$row = $db->exec($sql);
			return $row;
		}
		public function chaxunOne($table,$id){//数据库查询单条记录
			$sql = "SELECT * FROM ".$table." WHERE id=".$id;
			$db = $this->db;
			$sth = $db->query($sql);
			$row = $sth->fetch(PDO::FETCH_ASSOC);
			return $row;
		}
		public function chaxunAll($table){//数据库查询全部记录
			$sql = "SELECT * FROM ".$table;
			$db = $this->db;
			$sth = $db->query($sql);
			while ($row = $sth->fetch(PDO::FETCH_ASSOC)) {
				$arr[] = $row;
			}
			return $arr;
		}
	}
?>

<?php
	require "sql.php";
	$root = new mysqlSql(&#39;wanlala_1&#39;);
	//var_dump($root->chaxunAll(&#39;boke_wz&#39;));
	//var_dump($root->chaxunOne(&#39;boke_wz&#39;,2));
	//var_dump($root->zengjia(&#39;boke_wz&#39;,"是盛大发售","的飒飒是打算打算撒大大大是实打实的所说的是答案是"));
	//var_dump($root->shanchu(&#39;boke_wz&#39;,30));
	var_dump($root->gengxin(&#39;boke_wz&#39;,&#39;啊哈哈哈哈哈&#39;,&#39;尽快尽快尽快和交换机好就好&#39;,31));

?>