What is the difference between realpath() and is_dir() in php?

What is the difference between realpath($path) and is_dir($path)?

I know realpath follows symbolic links, but is ther开发者_JAVA技巧e a performance difference between the two?

Realpath returns the canonicalized actual pathname of a file on success, is_dir returns a boolean value of whether or not the file is a directory.

http://php.net/manual/en/function.is-dir.php
http://php.net/manual/en/function.realpath.php

How about looking at the manual.

realpath — Returns canonicalized absolute pathname

is_dir — Tells whether the filename is a directory