Eclipse Photon and Ubuntu 18.04 - DLTK indexing not working - eclipse

Question

I'm on Ubuntu 18.04 with JAVA openjdk 10.0.2 and Eclipse Photon (PHP edition).
DLTK Indexing seems to not work properly:
If I put my pointer on a PHP function , I have all documentation from PHP doc.
But if I put the pointer on any other functions (from symfony for example or on one of mine) nothing appears.
I have already check the build path and try to make a clean reinstall.
I also tried to delete files in : eclipse-workspace/.metadata/.plugins/org.eclipse.dltk.core.index.lucene/index
In eclipse logs, the only message I can't understand is :
java.lang.IllegalArgumentException: Maximum limit of resources to transfer is: 1000000
at org.eclipse.ui.part.ResourceTransfer.nativeToJava(ResourceTransfer.java:178)
at org.eclipse.swt.dnd.Clipboard.getContents(Clipboard.java:323)
at org.eclipse.swt.dnd.Clipboard.getContents(Clipboard.java:243)
at org.eclipse.ui.internal.navigator.resources.actions.PasteAction.lambda$0(PasteAction.java:187)
at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:236)
at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:147)
at org.eclipse.swt.widgets.Display.syncExec(Display.java:5941)
at org.eclipse.ui.internal.navigator.resources.actions.PasteAction.updateSelection(PasteAction.java:184)
at org.eclipse.ui.actions.BaseSelectionListenerAction.selectionChanged(BaseSelectionListenerAction.java:127)
at org.eclipse.ui.internal.navigator.resources.actions.EditActionGroup.updateActionBars(EditActionGroup.java:156)
at org.eclipse.ui.internal.navigator.resources.actions.EditActionProvider.updateActionBars(EditActionProvider.java:62)
at org.eclipse.ui.navigator.NavigatorActionService$3.run(NavigatorActionService.java:269)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
at org.eclipse.ui.navigator.NavigatorActionService.fillActionBars(NavigatorActionService.java:261)
at org.eclipse.ui.navigator.CommonNavigatorManager.selectionChanged(CommonNavigatorManager.java:220)
at org.eclipse.jface.viewers.Viewer$1.run(Viewer.java:158)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
at org.eclipse.ui.internal.JFaceUtil.lambda$0(JFaceUtil.java:47)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:176)
at org.eclipse.jface.viewers.Viewer.fireSelectionChanged(Viewer.java:155)
at org.eclipse.jface.viewers.StructuredViewer.updateSelection(StructuredViewer.java:2182)
at org.eclipse.jface.viewers.StructuredViewer.setSelection(StructuredViewer.java:1719)
at org.eclipse.jface.viewers.TreeViewer.setSelection(TreeViewer.java:1084)
at org.eclipse.ui.navigator.CommonViewer.setSelection(CommonViewer.java:373)
at org.eclipse.jface.viewers.Viewer.setSelection(Viewer.java:383)
at org.eclipse.wst.jsdt.internal.ui.packageview.PackageExplorerContentProvider$7.run(PackageExplorerContentProvider.java:1514)
at org.eclipse.wst.jsdt.internal.ui.packageview.PackageExplorerContentProvider.runUpdates(PackageExplorerContentProvider.java:198)
at org.eclipse.wst.jsdt.internal.ui.packageview.PackageExplorerContentProvider.runPendingUpdates(PackageExplorerContentProvider.java:190)
at org.eclipse.wst.jsdt.internal.ui.packageview.PackageExplorerContentProvider$1.runInUIThread(PackageExplorerContentProvider.java:168)
at org.eclipse.ui.progress.UIJob.lambda$0(UIJob.java:98)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:40)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:185)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:5026)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4586)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1173)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1062)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:156)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:628)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:563)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:151)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:155)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:199)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:137)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:107)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:391)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:246)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:659)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:595)
at org.eclipse.equinox.launcher.Main.run(Main.java:1501)
at org.eclipse.equinox.launcher.Main.main(Main.java:1474)
Thanks for your help
enuts