One of the most common reasons why you get 'No input file specified' (AKA 'the second most useful error message in the world') is that you have set 'doc_root' (in php.ini) to a value which is to the 'DocumentRoot' defined in the apache configuration.
This is the same for other webservers. For example, on lighttpd, make sure the 'server.document-root' value is the same as what is defined as 'doc_root' in php.ini.
