php cant find class if file name starts with a capital B -

i'm having trouble confusing error. have class , extended class. if extended file name starts capital b cannot find database class. if name else, literally else works.

my database class looks so

class database {     public $db;      public function __construct()      {         if (database == true)          {             $this->db = new mysqli(hostname, username, password, dbname);             if ($this->db->connect_error)              {                 exit('some of database login credentials seem wrong.' . '-' .  $this->db->connect_error);             }         }     } } 

my extended class so

class blogmodel extends database {     public function getblogposts()     {         $query = array();         if ($result = $this->db->query('select * blog'))          {             while ($row = $result->fetch_assoc())              {                 $query[] = $row;             }             $result->free();         }         return $query;         $mysqli->close();     } } 

the filename blogmodel.php causes error.

fatal error: class 'database' not found in c:\wamp\www\website\app\model\blogmodel.php on line 4 

if change blogmodel.php works. don't mind changing filename in interest of understanding , learning i'd know why happening.

edit: how include files

define('root', str_replace('\\', '/', $_server['document_root'])); define('host', $_server['http_host']);               define('url', $_server['request_uri']);              define('app', root . '/app/');   define('model', root . '/app/model/');                      define('view', app . '/view/');  define('controller', root . '/app/controller/');    $models = array_diff(scandir(model), array('.', '..')); foreach ($models $m)  {     require_once model . $m; } 

to use autoloader psr compliant need restructure directory tree.

the code use (not fully) psr-4 compliant code:

<?php     #cn class name     #fn file name     #ns namespace     #np namespace pointer      class loader{         public function load($class){             $cn = ltrim($class, '\\');             $fn = '';             $ns = '';              if($np = strrpos($cn, '\\')){                 $ns = substr($cn, 0, $np);                 $cn = substr($cn, $np + 1);                 $fn = str_replace('\\', directory_separator, $ns) . directory_separator;             }              require ($fn .= strtolower(str_replace('_', directory_separator, $cn)) . '.php');         }          public function __construct(){             spl_autoload_register([$this, 'load']);         }     }      new loader;  ?> 

it load files in lower case filename, if not use namespaces attempt load document root if object not exist.

if using namespaces, aka:

$var = new \path\to\object(); 

it attempt load object.php webroot\path\to\

how 1 use simple, include file , next time create object keep namespace valid path.