In some of the Harry Potter movies, the train guard at King's Cross station shouts something. It sounds like "Egg jewel on!"
Chamber of Secrets:
Must be some kind of railway slang, or maybe in a thick accent.
To me it sounds like he's yelling
"Stand clear o' th' doors!",
The conductor is warning people not to get in between the doors as they close
In a comment on the first video that was linked, user Requi says that the German translation of the film has the Conductor saying
"Get away from the platform."
I can't find a German translation of the script, and even in the original script there is no mention of a conductor saying anything in this scene.
He's saying ...
"[Please] Stand clear o'[f] th'[e] door[s]"
Which is a standard announcement on British rail services before departure to ensure that those boarding the train are out of harm's way before they move off.
On a related note, the doors on the Hogwarts Express are manually operated, so the guard is almost certainly shouting about a standard service train (one with powered doors operated by a conductor) on the next platform over.
Since the trains run on a schedule, it's not much of a coincidence that the same conductor is on platform 10 (or 9) a year later.