Mysql的底层封装

class db_mysql
{
	private $db;
	private $dbhost;//数据库主机名
	private $dbuser;//数据库用户名
	private $dbpw;//数据库密码
	private $dbname;//数据库名字
	private $pconnect;//0 =>不持久连接, 1=> 持久连接
	private $charset;//数据库编码
	var $query_num=0;//查询次数
			
	public function __construct($dbhost,$dbuser,$dbpw,$dbname,$pconnect=0,$charset="utf8")
	{
		$this->dbhost=$dbhost;
		$this->dbuser=$dbuser;
		$this->dbpw=$dbpw;
		$this->dbname=$dbname;
		$this->pconnect=$pconnect;
		$this->charset=$charset;
		$this->connect();//初始化数据库链接
	}
	//数据库链接
	private function connect()
	{
		if (!function_exists('mysql_connect')||!function_exists('mysql_pconnect')){
			$this->halt('服务器PHP不支持MySql数据库!');
		}	
		if(!empty($this->dbhost)|| !empty($this->dbuser)||$this->dbhost!=="" ||$this->dbuser!=="") {
			if($this->pconnect==1){
				$this->db=@mysql_pconnect($this->dbhost,$this->dbuser,$this->dbpw,true);
				if(!$this->db){
					$this->halt("数据库持久连接失败,可能是数据库用户名或密码错误！");
				}
			} else {
				$this->db=@mysql_connect($this->dbhost,$this->dbuser,$this->dbpw);
				if(!$this->db){
					$this->halt("数据库连接失败,可能是数据库用户名或密码错误！");
				}
			}
		} 
		if ($this->version() >'4.1'){
			mysql_query("set names ".$this->charset,$this->db);		
		}
		if(!empty($this->dbname)||$this->dbname!=""){
			if(!mysql_select_db($this->dbname,$this->db)){
				$this->halt("数据库选择失败,可能是数据库名错误！");
			}
		}
	}
	//查询执行
	function query($sql, $unbuffered = false)
	{
		$func = $unbuffered ? 'mysql_unbuffered_query' : 'mysql_query';
   		$query = @$func($sql);
		if(!$query){
			$this->halt('Query 错误
'.$sql);
		}
		$this->query_num++;
    	return $query;
	}
	//选择数据库
	function select_db($dbname) 
	{
		return mysql_select_db($dbname, $this->db);
	}
	//取单一数据(MYSQL_ASSOC,MYSQL_NUM,MYSQL_BOTH)
	function fetch($query, $result_type=MYSQL_ASSOC) 
	{
		return mysql_fetch_array($query, $result_type);
	}	
	//取结果集数据(MYSQL_ASSOC,MYSQL_NUM,MYSQL_BOTH)
	function fetch_array($query, $result_type=MYSQL_BOTH) 
	{
		return mysql_fetch_array($query, $result_type);
	}
	
	function fetch_row($query) 
	{
		return mysql_fetch_row($query);
	}
	
	function fetch_field($query) 
	{
		return mysql_fetch_field($query);
	}
	
	function fetch_assoc($query)
	{
		return mysql_fetch_assoc($squery);
	}
	//返回根据所取得的行生成的对象*
    function fetch_object($result)  
	{  
        return mysql_fetch_object($result);  
    } 
	//返回上次UPDATE更改的行数，上次DELETE删除的行数，或上次INSERT语句插入的行数。
	function affected_rows() 
	{
		return mysql_affected_rows($this->db);
	}
	//返回结果集
	function result($query, $row = 0, $field = 0) 
	{
		return  @mysql_result($query, $row, $field);
	}
	//释放结果集
	function free_result($query) 
	{
		return mysql_free_result($query);
	}

	//返回行数
	function num_rows($query) 
	{
		return mysql_num_rows($query);
	}
	//获得结果集中字段的数目
	function num_fields($query) 
	{
		return mysql_num_fields($query);
	}
	//返回插入的ID值
	function insert_id() 
	{
		return ($id = mysql_insert_id($this->db)) >= 0 ? $id : $this->result($this->query("SELECT last_insert_id()"), 0);
	}
	//错误信息
	function error() 
	{
		return (($this->db) ? mysql_error($this->db) : mysql_error());
	}
	//错误代码
	function errno() 
	{
		return intval(($this->db) ? mysql_errno($this->db) : mysql_errno());
	}
	//获取数据库版本
	function version() 
	{
		if(empty($this->version)) {
			$this->version = mysql_get_server_info($this->db);
		}
		return $this->version;
	}
	//列出 MySQL 数据库中的表
    function get_table_names($dbname='')
	{
		if(empty($dbname))
		{
			$db_name=$this->dbname;
		} else {
			$db_name=$dbname;
		}		
		$result = mysql_list_tables($db_name);
		$num_tables = @mysql_numrows($result);
		for ($i = 0; $i < $num_tables; $i++) {
			$tables[] = mysql_tablename($result, $i);
		}
		mysql_free_result($result);
		return $tables;
   	}
	function data_seek($result, $offset)
	{
		return mysql_data_seek($result, $offset);
	}	
	// 对特殊字符进行过滤value  值
	function escape_string($str){
		return mysql_real_escape_string($str,$this->db) or  mysql_real_escape_string($str);
	}
	//关闭数据库
	function close() {
		return mysql_close($this->db);
	}	
	//
	function get_client_info()
	{
		return mysql_get_client_info($this->db);
	}
	//
	function get_proto_info()
	{
		return mysql_get_proto_info($this->db);
	}
	//
	function get_host_info()
	{
		return mysql_get_host_info($this->db);
	}
	//
	function field_len($result, $i)
	{
		return mysql_field_len($result, $i);
	}
	//
	function field_name($result, $i)
	{
		return mysql_field_name($result, $i);
	}
	//
	function field_flags($result, $i)
	{
		return mysql_field_flags($result, $i);
	}
	//
	function get_fields_meta($result)
	{
		$fields       = array();
		$num_fields   = mysql_num_fields($result);
		for ($i = 0; $i < $num_fields; $i++) {
			$field = mysql_fetch_field($result, $i);
			$field->flags = mysql_field_flags($result, $i);
			$field->orgtable = mysql_field_table($result, $i);
			$field->orgname = mysql_field_name($result, $i);
			$fields[] = $field;
		}
		return $fields;
	}
	//错误提示
	private function halt($msg=&#39;&#39;)
	{
		$s=&#39;&#39;;
		$error = $this->error();
		$errorno = $this->errno();
		
		$s.="";	
		if($this->db){
			$Version=$this->version();
			$s.="".$Version."
";
		}
		$s.="".$msg."
";
		$s.="".$error."
";
		$s.="".$errorno."
";
		die($s);
	}

}