How does this "require" statement with a dynamic filepath work?

require dirname(__FILE__).'/yahooPHP/lib/Yahoo.inc';

This line is in one file in one directory and I am having trouble determining how to reference a file in another directory.

What does this expression mean and does it imply references must only be within the same directory?

__FILE__ is a Magic Constant that correspond to the full path to the file into which it is written.

This means that dirname(__FILE__) points to the directory into which your current file (the one in which this is written) is.

So, dirname(__FILE__).'/yahooPHP/lib/Yahoo.inc' points to :

• The directory into which this line is written,
• And, then, the yahooPHP subdirectory of that directory
• and the lib subdirectory of yahooPHP
• and the Yahoo.inc file into that lib directory.

Basically, you have :

your-file.php
yahooPHP/
    lib/
        Yahoo.inc