php连接mysql,mssql,oracle

dbtypedef.php
<?php
 // 数据库部分参数设置    
 @define("DATABASE_ACCESS",    0);
 @define("DATABASE_MSSQL",     1);
 @define("DATABASE_ORACLE",    2);
 @define("DATABASE_MYSQL",     3);
 @define("DATABASE_POSTGRESQL",4);
 @define("DATABASE_SQLITE",    5);
?>

/*==============================================================*/
/*   文件名称: Model.class.php                                   
/*   概要:    数据访问层数据库处理的公共父类模型).              */
/*   作者:
/*   创建时间: 2010-10-20    
/*==============================================================*/
class Model {
 protected $mysqli;    //
 protected $messList;  //提示信息列表
 protected $tabName;   //数据表
 protected $fieldList; //数据列表
 protected $oracle;    //数据列表

 public function __construct() {

if(DB_TYPE == DATABASE_MYSQL)
{   
    $this->mysqli = new mysqli ( DB_HOST, DB_USER, DB_PWD, DB_NAME );
    $this->mysqli->query("set names utf8");
    if (mysqli_connect_errno ()) {
       echo "" . mysqli_connect_error ();
       $this->mysqli = FALSE;
       exit();
    }
}
else if(DB_TYPE == DATABASE_MSSQL)
{
    $conn=mssql_connect(DB_HOST, DB_USER, DB_PWD)or die("Couldn't connect to SQL Server on ".DB_HOST.""); 
    mssql_select_db(DB_NAME,$conn);
    mssql_query("set names utf8");
}
else if(DB_TYPE == DATABASE_ORACLE)
{
    $ora_connstr = "(description=(address=(protocol=tcp) (host=".DB_HOST.")(port=".DB_PORT.")) (connect_data=(service_name=".DB_NAME.")))";
    $this->oracle = oci_connect(DB_USER, DB_PWD,$ora_connstr);
    if (!$this->oracle) {
       echo "oracle连接失败";
       $e = oci_error();
       trigger_error(htmlentities($e['message'], ENT_QUOTES), E_USER_ERROR); 
    }
 }
 }
}