What is the ruling on one who says the opening Takbir (Takbirat al-Ihram) to himself, or says part of it to himself?

If someone says the opening takbir (Allahu Akbar) to themselves, or does not move their tongue with it, either entirely or partially, then their prayer is not valid and they must repeat it. This is because the majority of scholars hold that the worshipper must hear themselves say the takbir. Some scholars, however, are of the view that merely moving the tongue is sufficient.