// menu
echo '<a href="index.php?aid=1">1st article</a><br />';
...
echo '<a href="index.php?aid=n">n-th article</a><br />';

// includeing article
if( file_exists('article_' . intval($_GET['aid']) . '.htm') ){
  include 'article_' . intval($_GET['aid']) . '.htm';
}
else{
   echo 'Choose an article from menu';
}

include 'footer.php';

switch($_GET['aid']){
   case 'valid_article_1':
      include('this_is_a_valid_article1.htm');
      break;
   case 'this_is_ok_too':
      include('blah_blah_blah.htm');
      break;
   case 'whatsniceaboutthis':
      include('is_thevar_doesnthaveanythingtodowithe_filename.htm');
      break;
   case 'default':
      die('That is an invalid article id');
}

//clean variable
$pattern= array('@<script[^>]*?>.*?</script>@si',       // Strip out javascript
            '@<[\/\!]*?[^<>]*?>@si');              // Strip out HTML tags
$aid = preg_replace($pattern,"",trim($_GET['aid']));
if(!get_magic_quotes_gpc()){ $aid = addslashes($aid); }

//built a select statement
$select = "SELECT article_title, article_text, author, date FROM table WHERE short_name='$aid'";

//connect to the database and select the db and all that other crap
include('connect.php');

//query the database
unset($result);
$result = mysql_query($select);
if(!$result){
   echo 'That article doesn\'t exist.';
}
else{
   while($row = mysql_fetch_array($result)){
      echo '<center><h1>';
      echo $row['article_title'];
      echo '</h1><br>';
      echo $row['author'];
      echo '</center><br><Br>';
      echo nl2br($row['article_text']);
      echo '<br><br>';
   }
}