is config.php bad filename?
<p>This examples are from lynda php beyond basic</p>

<p><strong>config.php</strong></p>

<pre><code>&lt;?php
    defined('DB_SERVER') ? null : define("DB_SERVER", "localhost");
    defined('DB_USER')   ? null : define("DB_USER", "root");
    defined('DB_PASS')   ? null : define("DB_PASS", "");
    defined('DB_NAME')   ? null : define("DB_NAME", "photo_gallery");
?&gt;
</code></pre>

<p><strong>database.php</strong></p>

<pre><code>&lt;?php
require_once('config.php');

class MySQLDatabase {

private $connection;

function __construct(){
    $this-&gt;open_connection();
}

public function open_connection(){
    $this-&gt;connection = mysql_connect(DB_SERVER, DB_USER, DB_PASS);

    if (!$this-&gt;connection) {
        die("Database connection failed: " . mysql_error());
    } else {
        $db_select = mysql_select_db(DB_NAME, $this-&gt;connection);

        if (!$db_select) {
            die("Database selection failed: " . mysql_error());
        }
    }
}

public function close_connection(){

    if(isset($this-&gt;connection)) {
        mysql_close($this-&gt;connection);
        unset($connection);
    }
}

public function query($sql) {
    $result = mysql_query($sql, $this-&gt;connection);
    $this-&gt;confirm_query($result);
    return $result;
}



private function confirm_query($result){
    if (!$result) {
        die("Database query failed: " . mysql_error());
    }   
}
}

$database = new MySQLDatabase();

?&gt;
</code></pre>

<p><strong>index.php</strong></p>

<pre><code>&lt;?php
    require_once("../includes/database.php");

    if (isset($database)) {
        echo "true";
    } else {
        echo "false";
    }

?&gt;
</code></pre>

<p>Now here my problem when I tried index.php run it on the browser i get an error
error says:</p>

<blockquote>
  <p>Deprecated: Assigning the return value of new by reference is deprecated in C:\xampp\php\PEAR\Config.php on line 80</p>
  
  <p>Deprecated: Assigning the return value of new by reference is deprecated in C:\xampp\php\PEAR\Config.php on line 166</p>
  
  <p>Notice: Use of undefined constant DB_SERVER - assumed 'DB_SERVER' in C:\xampp\htdocs\photo_gallery\includes\database.php on line 13</p>
  
  <p>Notice: Use of undefined constant DB_USER - assumed 'DB_USER' in C:\xampp\htdocs\photo_gallery\includes\database.php on line 13</p>
  
  <p>Notice: Use of undefined constant DB_PASS - assumed 'DB_PASS' in C:\xampp\htdocs\photo_gallery\includes\database.php on line 13</p>
  
  <p>Warning: mysql_connect() [function.mysql-connect]: php_network_getaddresses: getaddrinfo failed: No such host is known. in C:\xampp\htdocs\photo_gallery\includes\database.php on line 13</p>
  
  <p>Warning: mysql_connect() [function.mysql-connect]: [2002] php_network_getaddresses: getaddrinfo failed: No such host is known. (trying to connect via tcp://DB_SERVER:3306) in C:\xampp\htdocs\photo_gallery\includes\database.php on line 13</p>
  
  <p>Warning: mysql_connect() [function.mysql-connect]: php_network_getaddresses: getaddrinfo failed: No such host is known. in C:\xampp\htdocs\photo_gallery\includes\database.php on line 13
  Database connection failed: php_network_getaddresses: getaddrinfo failed: No such host is known.</p>
</blockquote>

<p>I somehow fix the error by renaming config.php</p>

<p>So here's my question why i got this error? is config.php filename the problem? 
The video tutorial from Lynda php beyond basics didn't get this error.</p>
