BEWARE!
Like Hayley Watson pointed out class names are not case sensitive.
<?php
class Foo{}
class foo{} ?>
As well as
<?php
class BAR{}
$bar = new Bar();
echo get_class($bar);
?>
Is perfectly fine and will return 'BAR'.
This has implications on autoloading classes though. The standard spl_autoload function will strtolower the class name to cope with case in-sensitiveness and thus the class BAR can only be found if the file name is bar.php (or another variety if an extension was registered with spl_autoload_extensions(); ) not BAR.php for a case sensitive file and operating system like linux. Windows file system is case sensitive but the OS is not and there for autoloading BAR.php will work.
