How to determine what macport (if any) containing an specific file?
Answer from Stackoverflow:


  Unfortunately MacPorts currently (2.3.1) only supports that if you have the port installed, i.e. if you want to find out which port installed a file on your system. In this case, you can use port provides .


The answer also suggests to use a Linux distribution (e.g. Debian) to search for the file and choose a similar Macports port with the found Debian package name:

Here is a search engine for Debian: search package content

Example:
Result for ".../sapi/embed/php_embed.h":

File                                        Packages
/usr/include/php5/sapi/embed/php_embed.h    php5-dev