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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='')	{		$s='';		$error = $this->error();		$errorno = $this->errno();				$s.="";			if($this->db){			$Version=$this->version();			$s.="".$Version."";		}		$s.="".$msg."";		$s.="".$error."";		$s.="".$errorno."";		die($s);	}}

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