(no version information, might be only in CVS)
PharFileInfo->setMetaData -- Sets file-specific meta-data saved with a filesetMetaData() should only be used to store customized data in a file that cannot be represented with existing information stored with a file. Meta-data can significantly slow down the performance of loading a phar archive if the data is large, or if there are many files containing meta-data. It is important to note that file permissions are natively supported inside a phar, although it is possible to set them with the PharFileInfo->chmod() method. As with all functionality that modifies the contents of a phar, the phar.readonly INI variable must be off in order to succeed.
Some possible uses for meta-data include passing a user/group that should be set when a file is extracted from the phar to disk. Other uses could include explicitly specifying a MIME type to return. However, any useful data that describes a file, but should not be contained inside of it may be stored.