setMetaData() should only 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 significantly slow down the performance of loading a phar archive if the data is large. 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 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.
Any PHP variable containing information to store that describes the phar archive
Example 1. A Phar->setMetaData() example
The above example will output: