I am installing the PHP Development Toolkit for Eclipse (PDT) and received this error:
"Cannot complete the install because one or more required items could not be found. Software being installed: PHP Development Tools (PDT) Mylyn Integration 188.8.131.52409161013 (org.eclipse.php.mylyn.feature.group 184.108.40.206409161013) Missing requirement: PHP Development Tools (PDT) Mylyn Integration 220.127.116.11409161013 (org.eclipse.php.mylyn.feature.group 18.104.22.168409161013) requires 'org.eclipse.dltk.mylyn.feature.group 0.0.0' but it could not be found"
The error is due to my Eclipse installation missing org.eclipse.dltk.mylyn.feature.group 0.0.0, obviously. The gotcha is that it should be readily available from one of the update sites listed in the Install New Software dialog, however, it is not. To fix this error, add http://download.eclipse.org/technology/dltk/updates-dev/5.0/ to your update sites and retry the install.