site root relative path confusion in php - php

Question

I'm trying to upload images to server, create a thumbnail from the uploaded image, and save the relative paths to mysql database . . . . The image path is
/mysite/images/
from my site root (which is wamp/www/mysite/images in my local testing environment)
Now, I'm performing a directory check with
if(!is_dir($path) && !is_writable($path)){
throw new Exception ("$path is not valid .. ");
}
where path is /mysite/images/ , thinking that initial '/' will denote the root.
But, the script was throwing an exception saying invalid path name, and my
move_uploaded_file($tmp_name, $path.$filename)
too was not working.
PS: the path mysite/images/ also throws an error and the file is not moved
Now, I have worked around by appending document root manually to path name for both directory checks and move file , which is now looking like
if(!is_dir($_SERVER['DOCUMENT_ROOT'].$path) && !is_writable($_SERVER['DOCUMENT_ROOT'].$path)){
throw new Exception ("$path is not valid .. ");
}
move_uploaded_file($tmp_name, $_SERVER['DOCUMENT_ROOT'].$path.$filename)
I also changed the path to
mysite/images/
removing the initial slash intended for site root. This is working perfectly.
But, I cannot understand why directory check and move uploaded file snippets are not taking site root relative links.
Any ideas is appreciated.

Answer 1

The problem is with the path representation.
In linux /mysite will try to access the directory in the root level of file system. Windows this might not create an error. for is_file() kind of API's it should the absolute path and not relative ones.

Answer 2

Your website path is not wamp/www/mysite/images.
You are using a web server, you cant access the drive like: c:/wamp ....
Once online, how will you access your files? Linux does not have c:/ ...
Your website path is: http://localhost/mysite/
Your image path is: http://localhost/mysite/images or ./images if your code is correctly written.
so, do this:
define('ROOT', $_SERVER['DOCUMENT_ROOT']);
include_once(ROOT."/mycfgfile.php");
or
include_once(ROOT."/includes/mycfgfile.php");