Q: All of a sudden  no sound comes out of my iPhone 4s not even with earphones in

Try to reset your device. This won't delete your data stored on the phone.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

If this does not help take your phone to the Apple Store.

Make sure there is no debris or fluff in the headphone socket .That can mimic the presence of Headphones and cut off speaker sound

and check through this

If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker - Apple Support