Er, you should not be using the 2 types of special quotes for string quoting in PHP.
You should be typing
include_once('/full/path/to/app');
( That's ASCII character 39 )
This is not what it says at the end of
this document:
www.wpbbpthemes.org/integration/
"beware some pasting of this code make
the ‘ character change, make sure it’s
the button left of the enter key on
your [US] keyboard"
No, you are misinterpreting it. Lots of software in windows, and varying keyboards, erroneously do "smart quotes". Word and Internet Explorer are such examples. As a result, copy-pasting from these applications results in the wrong type of character in your source code, often conflicting with the content-encoding the document is served as, which renders on the displaying browser as a silly Ä or similar character.
Do not use characters 145 and 146 in your PHP source, it is not necessary, and it won't work.
Also, Important to note, the authors of that page have USED THE WRONG QUOTES IN THEIR EXAMPLES and as such, WILL NOT WORK AS STATED.
Their statement with regard to "beware some pasting will make the character change" is bogusly incorrect, they have the incorrect character in their source, and as such, copy-pasting it at any time will not work.