If you get the following message when installing Phoca Gallery: JInstaller: :Install: Cannot find Joomla XML setup file, then it seems like your server has a limitation in that, it can only extract or create archives with less files than your OS's file handle limit. Phoca Gallery is large component which includes more files than your server is able to unpack (due to the limitation). In such case, please upload extracted files to your server, to e.g. folder: tmp/phocagallery and use Joomla's Install from Directory feature.
1) Create a folder inside tmp folder in your Joomla! root: tmp/phocagallery (with help of FTP client or some file manager).
2) Extract Phoca Gallery Installation ZIP file on your PC and copy all the files (with help of FTP) to your server, to tmp/phocagallery folder.
3) In your Joomla! administration, navigate to Extensions - Manage - Install. Click the second tab Install from Folder
Set the right path in form field: Install from Folder . E.g. to /your-path/your-joomla/tmp/phocagallery
4) Click on Check and Install button. After installation, don't forget to remove the files in folder tmp/phocagallery (include phocagallery folder).