具体实现代码如下:

class DB_Sql { 

  var $Host     = "";
  var $Database = "";
  var $User     = "";
  var $Password = "";
  var $Link_ID  = 0;
  var $Query_ID = 0;
  var $Record   = array();
  var $Row      = 0;
  
  var $Errno    = 0;
  var $Error    = "";
  var $Auto_Free = 0;     ## set this to 1 to automatically free results
  
  function DB_Sql($query = "") {
      $this->query($query);
  }
  function connect() {
    if ( 0 == $this->Link_ID ) {
      $this->Link_ID=mssql_connect($this->Host, $this->User, $this->Password);
      if (!$this->Link_ID)
        $this->halt("Link-ID == false, mssql_pconnect failed");
      else
          @mssql_select_db($this->Database, $this->Link_ID);
    }
  }
  function free_result(){
      mssql_free_result($this->Query_ID);
      $this->Query_ID = 0;
  }
  
  function query($Query_String) 
  {
    
    /* No empty queries, please, since PHP4 chokes on them. */
    if ($Query_String == "")
      /* The empty query string is passed on from the constructor,
       * when calling the class without a query, e.g. in situations
       * like these: '$db = new DB_Sql_Subclass;'
       */
      return 0;
      if (!$this->Link_ID)
        $this->connect();
    
#   printf("
Debug: query = %s
", $Query_String);
 
 $this->Query_ID = mssql_query($Query_String, $this->Link_ID);
    $this->Row = 0;
    if (!$this->Query_ID) {
      $this->Errno = 1;
      $this->Error = "General Error (The MSSQL interface cannot return detailed error messages).";
      $this->halt("Invalid SQL: ".$Query_String);
    }
    return $this->Query_ID;
  }
  
  function next_record() {
      
    if ($this->Record = mssql_fetch_row($this->Query_ID)) {
      // add to Record[]
      $count = mssql_num_fields($this->Query_ID);
      for ($i=0; $i<$count; $i++){
          $fieldinfo = mssql_fetch_field($this->Query_ID,$i);
        $this->Record[strtolower($fieldinfo->name)] = $this->Record[$i];
      }
      $this->Row += 1;
      $stat = 1;
    } else {
      if ($this->Auto_Free) {
            $this->free_result();
          }
      $stat = 0;
    }
    return $stat;
  }
  
  function seek($pos) {
        mssql_data_seek($this->Query_ID,$pos);
      $this->Row = $pos;
  }
  function metadata($table) {
    $count = 0;
    $id    = 0;
    $res   = array();
    $this->connect();
    $id = mssql_query("select * from $table", $this->Link_ID);
    if (!$id) {
      $this->Errno = 1;
      $this->Error = "General Error (The MSSQL interface cannot return detailed error messages).";
      $this->halt("Metadata query failed.");
    }
    $count = mssql_num_fields($id);
    
    for ($i=0; $i<$count; $i++) {
        $info = mssql_fetch_field($id, $i);
      $res[$i]["table"] = $table;
      $res[$i]["name"]  = $info["name"];
      $res[$i]["len"]   = $info["max_length"];
      $res[$i]["flags"] = $info["numeric"];
    }
    $this->free_result();
    return $res;
  }
  
  function affected_rows() {
// Not a supported function in PHP3/4.  Chris Johnson, 16May2001.
//    return mssql_affected_rows($this->Query_ID);
    $rsRows = mssql_query("Select @@rowcount as rows", $this->Link_ID);
    if ($rsRows) {       
       return mssql_result($rsRows, 0, "rows");
    }
  }
  
  function num_rows() {
    return mssql_num_rows($this->Query_ID);
  }
  
  function num_fields() {
    return mssql_num_fields($this->Query_ID);
  }
  function nf() {
    return $this->num_rows();
  }
  
  function np() {
    print $this->num_rows();
  }
  
  function f($Field_Name) {
    return $this->Record[strtolower($Field_Name)];
  }
  
  function p($Field_Name) {
    print $this->f($Field_Name);
  }
  
  function halt($msg) {
    printf("Database error: %s
", $msg);
    printf("MSSQL Error: %s (%s)
",
      $this->Errno,
      $this->Error);
    die("Session halted.");
  }
}