As Thomas Weidner mentions in a new blog post, starting with the 1.10 release of the Zend Framework there'll be a new component to help with compressing and decompressing files - Zend_Filter_Compress/Decompress.

The new components Zend_Filter_Compress and Zend_Filter_Decompress provide a unified API for several compression formats. Actually the formats BZ2, GZ, LZF, RAR, TAR and ZIP are implemented: You can not only work with Strings, but also with Files and also with complete Directories.

He includes a quick example of how it will work with both data (like a string) and writing out the information to a compressed file. You can find out more about the component from Thomas' proposal on the Zend Framework wiki.