正在学习PHP OOP，写了一个数据库操作类，有问题，希望大牛们指点一下。

[看小雪]

@xuzuning

<?php
/**
 * 数据库PDO操作
 * 注：使用此文件前，需要定义数据库的基本信息
 * $dsn = 'mysql:host=127.0.0.1;port=3333;dbname=testdb', $username, $userpwd;
 */
class class_db  {
	private  $statement  = null;  //PDOStatment

    private  $conn		 = null;  //单件模式,保存Pdo类唯一实例,数据库的连接资源
   
    public	 $lastSql 	 = '';    //当前SQL语句
   
    public   $error 	 = '';    //错误信息

    private  $lastInsertId = null;    //最后插入记录的ID

    private  $numRows 	   = 0;    //返回影响记录数

	public function __construct($dsn, $username, $userpwd){
		if (!class_exists('PDO')) throw_exception("not support:PDO");
		
		if(empty($dsn)) throw_exception("Please config DSN");
		
		if(is_object($this->conn)) {
			return $this->conn;
		}
		
		//$attrConfig = array('PDO::ATTR_PERSISTENT'=>true, 'PDO::ATTR_EMULATE_PREPARES'=>false,);
		try {
			$this->conn = new PDO($dsn, $username, $userpwd);
			$this->conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC); 
		}catch(PDOException $e){
			throw_exception($e->getMessage());
		}

		if(!$this->conn) throw_exception('PDO CONNECT ERROR');
		
		$this->conn->exec('SET NAMES utf8');
		$this->conn->exec('SET CHARACTER SET utf8'); 
		
		return $this->conn;
	}
	
	//开始查询
	public function query($sql)
	{
		if(empty($sql)){
			return $this->error = 'empty sql!';
        }
		$this->lastSql = $sql;
		try{
        	$this->statement = $this->conn->query($sql);
        	return $this->statement;
		}catch(Exception $e){
			$t  = $this->conn->errorInfo();
			$this->error = $t[2];
			return false;
		}
	}
	
	public function prepare($sql)
	{
		if(empty($sql)){
			return $this->error = 'empty sql!';
        }
		$this->lastSql = $sql;
		try{
        	$this->statement = $this->conn->prepare($sql);
        	return $this->statement;
		}catch(Exception $e){
			$t  = $this->conn->errorInfo();
			$this->error = $t[2];
			return false;
		}
	}
	
	//获取一条数据，返回一维数组
	public function fetch()
	{
		try{
			return $this->statement->fetch();
        }catch(Exception $e){
			$t  = $this->conn->errorInfo();
			$this->error = $t[2];
			return false;
		}
	}
	
	//获取多条数据，返回二维数组
	public function fetchAll()
	{
		try{
			return $this->statement->fetchAll();
        }catch(Exception $e){
			$t  = $this->conn->errorInfo();
			$this->error = $t[2];
			
			return false;
		}
	}
	
	//返回一个表字段内容
	public function fetchColumn($intColumn = 0)
	{
		try{
			return $this->statement->fetchColumn($intColumn);
        }catch(Exception $e){
			$t  = $this->conn->errorInfo();
			$this->error = $t[2];
			
			return false;
		}
	}
	
	//执行sql语句，主要用于无状态更新
	public function exec($sql)
	{
        try{
			$this->numRows = $this->conn->exec($sql);
            return $this->numRows;
        }catch(Exception $e){
			$t  = $this->conn->errorInfo();
			$this->error = $t[2];
			
            return false;
        }
    }
	
	//插入数据后的ID
	public function lastInsertId()
	{
		return $this->conn->lastInsertId();
	}
	
	//
	public function execute($param = ""){
        if(is_array($param)){
            try{
                return $this->statement->execute($param);
            }catch (Exception $e){
				$t  = $this->conn->errorInfo();
				$this->error = $t[2];
                return false;
            }
        }
        try{
            return $this->statement->execute();
        }catch(Exception $e){
			$t  = $this->conn->errorInfo();
			$this->error = $t[2];
            return false;
        }
    }
	
	//受影响的行数
	public function rowCount(){
        return $this->numRows;
    }
	
	/* 
 		$table 表名，string
		$arrayData，字段与数据, 一维array
	*/
	public function insert($table, $arrayData){
			if(empty($table) || !is_array($arrayData)){
				$this->error = 'insert:data is not array or table is not exists!';
				return false;
			}
			$vals = array_keys($arrayData);
			$cols = array();
			/*
			$arrayobject  = new  ArrayObject( $arrayData );
			$iterator     =  $arrayobject->getIterator();
			while($iterator->valid()) {
				$vals[] =  ':' . $iterator->key() . '';
				$iterator->next();
			}
			*/
			$c      = implode('', $vals);
			$cols   = array_filter(explode(':', $c));
	 
			$sql  = "INSERT INTO {$table} (";
			$sql .= implode(",", $cols) . ") VALUES (";       
			$sql .= implode(",", $vals) . ")";
			
			$this->lastSql = $sql;
			try{
				$this->statement = $this->conn->prepare($sql);
				$this->statement->execute($arrayData);
				return  $this->lastInsertId = $this->conn->lastInsertId();
			}catch(Exception $e){
				$t  = $this->conn->errorInfo();
				$this->error = $t[2];
            	return false;
			}
	}

	/* 
 		$table表名，string
		$fields要更新的字段，string
		$where 条件，string
	*/
	public function update($table, $fields, $where){
        if(empty($table) || empty($fields) || empty($where)){
			$this->error = 'update:data is not array!';
            return false;
        }
		
		$sql	= 'update '.$table.' set  ' . $fields. '  where  '. $where;
		
		$this->lastSql = $sql;
		try{
			$this->statement = $this->conn->prepare($sql);
			$this->statement->execute();
			return $this->numRows = $this->statement->rowCount();
		}catch(Exception $e){
			$t  = $this->conn->errorInfo();
            $this->error = $t[2];
			return false;
		}
    }
	
	/* 
 		$table表名,string
		$where删除数据条件，一维array
	*/
	public function delete($table, $where){
        if(empty($table) || empty($where) || !is_array($where)){
			$this->error = 'delete:data is not array or table is not exists!';
            return false;
        }
		$sql   = 'delete from '.$table.'  where ';
		
		$cols = array();
		$vals = array_keys($where);
		$c    = implode('', $vals);
		$cols = array_filter(explode(':', $c));

		$arr  = array_combine($cols, $vals);
		$i	  = 0;
		$sql1 = '';
		foreach($arr as $k => $v){
			$t = ($i > 0) ? ' and ' : ' ';
			$sql1 .= $t . ' ' . $k . '='. $v;
			$i += 1;
		}
		$sql .= $sql1;
		
		$this->lastSql = $sql;
		try{
        	$this->statement = $this->conn->prepare($sql);
        	$this->statement->execute($where);
        	return $this->numRows = $this->statement->rowCount();
		}catch(Exception $e){
			$t  = $this->conn->errorInfo();
            $this->error = $t[2];
			return false;
		}
    }
}
 ?>

版主，各位大牛，帮忙看看，这个类有缺点。类里面的fetch,fetchAll,fetchColumn没执行。


$db = new class_db('mysql:host=127.0.0.1;port=3306;dbname=test', 'root', '123456');

$sql = 'create table if not exists ttt (id int primary key auto_increment, title varchar(100), sort int)';
$db->exec($sql);
echo "<hr>";
echo '添加数据：'."<br>";
$data = array(':title'=>'山东红富士'.rand(1,100), ':sort'=>1);
$c = $db->insert('ttt', $data);
echo ($c > 0) ? "OK" : '添加数据失败',"<hr>";
if(empty($c))exit();

echo '获取一条数据：',"<br><pre>";
$sql = 'select * from ttt where id='.$c;
$rs = $db->query($sql)->fetch();
print_r($rs);
echo "<hr>";
exit;


我的意图在于组里所有的人都用此类，以后代码看起来统一一些，也能防止有些人偷懒，在添加数据的时候，拼接SQL语句，导致注入。目前似乎发现fetch,fetchAll,fetchColumn有问题，就是没执行，执行的是PDO的，不是我写的这个。

[xuzuning]

class_db::query 方法返回的是 PDOStatement 对象（54行 return $this->statement;） 所以 $rs = $db->query($sql)->fetch(); 这个是 PDOStatement 的方法 如果你需要是 class_db::fetch，那么 54 行处应 return $this;

[看小雪]

@xuzuning 我如果这样用是不是一个单例模式，访问效率是不是会比较的差？ 希望更多的人指毛病，找问题。