Set the default html browser via command line

An example Chromium Browser:

An example Firefox:
gvfs-mime --set x-scheme-handler/http firefox.desktop
gvfs-mime --set x-scheme-handler/https firefox.desktop

An example Opera:
gvfs-mime --set x-scheme-handler/http opera.desktop
gvfs-mime --set x-scheme-handler/https opera.desktop

PS. WordPress shown the command wrong, so read the right command here