Note: This
method requires the php.ini setting phar.readonly to be
set to 0 in order to work for Phar
objects. Otherwise, a PharException will be thrown.
Phar::setMetadata() should be used to store customized data
that describes something about the phar archive as a complete entity.
PharFileInfo::setMetadata() should be used for file-specific meta-data.
Meta-data can slow down the performance of loading a phar archive if the data is large.
Some possible uses for meta-data include specifying which file within the archive
should be used to bootstrap the archive, or the location of a file manifest
like » PEAR's package.xml file.
However, any useful data that describes the phar archive may be stored.
Parameters
metadata
Any PHP variable containing information to store that describes the phar archive