It seems that both the GLO and PHR file types serve same or similar purpose in Adobe RoboHelp so there might a chance that they can be, at least partially, converted between each other. However, this could not be exactly verified.
Convert Adobe RoboHelp glossary file to Adobe RoboHelp phrase file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert glo to phr on Windows
Professional tool for creating help documentation
Convert from glo file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.