Suddenly the autocompletion in my Eclipse PHP-project was not working anymore. I tried to restart Eclipse, clean and rebuild my projects but nothing worked. Until I found out the brute force solution: remove the index files autocomplete uses!
1. Just delete folder in from your workspace: /.metadata/.plugins/org.eclipse.dltk.core.index.sql.h2
2. Restart Eclipse
Note: If the autocomplete has never worked in your setup, perhaps you have not enabled it? To check and enable autocomplete, go to Eclipse menu: Window > Preferences > PHP > Editor > Content Assist and select "Enable auto activation".