$connection=mysql_connect($db_host,$db_username,$db_password);

$db_select=mysql_select_db($db_database);

mysql_query("set names 'utf8'");//编码
$result=mysql_query($sqlstring);

mysql_fetch_array($result);
mysql_fetch_row($result);

mysql_close($connection);

<?php
class DBHelper
{
  //建立连接
  function GetConnection($db_host,$db_username,$db_password)
  {
    $connection=mysql_connect($db_host,$db_username,$db_password);
    if($connection==false)
      die("数据库连接失败：".mysql_error());//输入具体错误信息
    return $connection;
  }
  //选择对应数据库
  function DBSelect($db_database)
  {
    $db_select=mysql_select_db($db_database);
    if($db_select==false)
      die("数据库选择失败：".mysql_error());
    return $db_select;
  }
  //执行CRUD操作
  function Excute($sqlstring)
  {
    $result=mysql_query($sqlstring);
    return $result;
  }
  //释放资源
  function CloseConnection($connection)
  {
    if($connection!=null)
    mysql_close($connection);
  }
}
?>

<?php
$db_host="localhost";
$db_database="mymessage";
$db_username="root";
$db_password="123456";
?>