Incompatible with PHP 5.5

This plugin doesn’t work with WP 3.9.1 and PHP 5.5. It fails when parsing a fetched feed because the call to apply_filters() chokes while trying to invoke the SyndicatedPost object’s resolve_relative_uris method.

Downgrading to PHP 5.3 got it working again.

https://wordpress.org/plugins/feedwordpress/