Given a string containing a path to a file, this function will return the name of the directory.
On Windows, both slash (/) and backslash (\) are used as directory separator character. In other environments, it is the forward slash (/).
Note: In PHP 4.0.3, dirname() was fixed to be POSIX-compliant. Essentially, this means that if there are no slashes in
path, a dot ('.') is returned, indicating the current directory. Otherwise, the returned string is
pathwith any trailing /component removed. Note that this means that you will often get a slash or a dot back from dirname() in situations where the older functionality would have given you the empty string.
dirname() has changed its behaviour in PHP 4.3.0. Check the following examples:
dirname() has been binary safe since PHP 5.0.0