php 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 $query_num=0;//查询次数
    //开始后直接执行           
    public function __construct($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){
            $this->halt('Query 错误<br>'.$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();

        $s.="<title>数据库错误提示</title>";   
        if($this->db){
            $Version=$this->version();
            $s.="<b>数据库版本信息：</b>".$Version."<br>";
        }
        $s.="<b>错误详情：</b>".$msg."<br>";
        $s.="<b>错误原因：</b>".$error."<br>";
        $s.="<b>错误代码：</b>".$errorno."<br>";
        die($s);
    }

}
//该片段来自于http://outofmemory.cn