All versions of PHP. Explicitly using file:// since PHP 5.0.0.
/path/to/file.ext
relative/path/to/file.ext
fileInCwd.ext
C:/path/to/winfile.ext
C:\path\to\winfile.ext
\\smbserver\share\path\to\winfile.ext
file:///path/to/file.ext
Filesystem is the default wrapper used with PHP and represents the local filesystem.
When a relative path is specified (a path which does not begin with /, \, \\, or a Windows drive letter)
the path provided will be applied against the current working directory. In many cases this is the
directory in which the script resides unless it has been changed. Using the CLI sapi, this defaults
to the directory from which the script was called.
With some functions, such as fopen() and file_get_contents(),
include_path may be optionally searched for relative paths as well.