Question: This is a philosophical question, actually.
It's been a year I'm programming using PHP as a language and, as all of you know, PHP is very liberal as for the datatypes.
I was wondering: given that, is it a good practice to allow methods to return different kind of values?
Example: I'm used to set the variable that should be returned at a default value (usually false) and, if during the execution of the method everything goes well, the variable gets the value the successful execution has given.
Disclaimer: I try to document everything using PHPDoc.

Answer: 
Seems like a correct approach: returning boolean false allows the method/function to return other logical "false" values such as 0 or the empty string as valid while still allowing the caller to check its result with the `===` operator.
It's a common approach, at least in PHP, and it isn't a bad practice.

It can be documented without problem using the PHPDoc convention: <http://manual.phpdoc.org/HTMLSmartyConverter/HandS/phpDocumentor/tutorial_tags.return.pkg.html>