With SplFileInfo:
SplFileInfo The SplFileInfo class offers a high-level object oriented
interface to information for an individual file.
Ref: http://php.net/manual/en/splfileinfo.getfilename.php
$info = new SplFileInfo('/path/to/foo.txt');
var_dump($info->getFilename());
o/p: string(7) "foo.txt"