I just had to upgrade my xdebug and though I might list my experience here in case others have a problem with it.
because pecl doesn't seem to work right in MAMPP, I had to follow the "install from source" directions. http://xdebug.org/docs/install
you have to explicitly give MAMPP's php-config, or else it will use the default Mac OS X one ...
./configure --enable-xdebug --with-php-config=/Applications/xampp/xamppfiles/bin/php-config
but this only halfway works. you still need to make this modification to the generated Makefile (and you have to have the xampp "developer package" installed):
INCLUDES = -I/Applications/xampp/xamppfiles/include -I/Applications/xampp/xamppfiles/include/php/php5/php -I/Applications/xampp/xamppfiles/include/php/php5/php/main -I/Applications/xampp/xamppfiles/include/php/php5/php/TSRM -I/Applications/xampp/xamppfiles/include/php/php5/php/Zend -I/Applications/xampp/xamppfiles/include/php/php5/php/ext -I/Applications/xampp/xamppfiles/include/php/php5/php/ext/date/lib
basically, you need to manually add the:
-I/Applications/xampp/xamppfiles/include
after that, you should be able to make, and then follow the rest of the xdebug install instructions.
think the explicit php-config and/or the extra include could go towards fixing pecl as bundled with xampp? would be great to have pecl work "out of the box"