mysql数据库连接类

mysql教程数据库教程连接类
 本文章提供一款完美的php教程 mysql数据库连接类程序，实例简单。

*/
class db{

var $linkid;
var $sqlid;
var $record;

function db($host="",$username="",$password="",$database="")
{
if(!$this->linkid)    @$this->linkid = mysql_connect($host, $username, $password) or die("连接服务器失败.");
@mysql_select_db($database,$this->linkid) or die("无法打开数据库");
return $this->linkid;}

function query($sql)
{if($this->sqlid=mysql_query($sql,$this->linkid)) return $this->sqlid;
else {
    $this->err_report($sql,mysql_error);
return false;}
}

function nr($sql_id="")
{if(!$sql_id) $sql_id=$this->sqlid;
return mysql_num_rows($sql_id);}

function nf($sql_id="")
{if(!$sql_id) $sql_id=$this->sqlid;
return mysql_num_fields($sql_id);}

function nextrecord($sql_id="")
{if(!$sql_id) $sql_id=$this->sqlid;
if($this->record=mysql_fetch_array($sql_id))    return $this->record;
else return false;
}

function f($name)
{
if($this->record[$name]) return $this->record[$name];
else return false;
}

function close() {mysql_close($this->linkid);}

function lock($tblname,$op="write")
{if(mysql_query("lock tables ".$tblname." ".$op)) return true; else return false;}

function unlock()
{if(mysql_query("unlock tables")) return true; else return false;}

function ar() {
      return @mysql_affected_rows($this->linkid);
    }

function i_id() {
    return mysql_insert_id();
}

function err_report($sql,$err)
{
echo "mysql查询错误<br>";
echo "查询语句：".$sql."<br>";
echo "错误信息：".$err;
}