Try restarting you iPhone by holding down the on/off and the home buttons at the same time until you see the Apple logo. If you are still having problems try putting your head phone jack in and out rapidly a few times. If you purchased your iPhone 6 months ago it is still under warranty if you are in the US.
This happened to me also. iPhone 4s. 6.1.3. Verizon. Speakerphone stopped working during a phone call. Speaker phone icon was lit. Person on other side of call could listen in. But no sound from speaker. Music doesn't play. Siri disappeared although she returned temporarily after I did a restore to new phone and then she went away again. What I've tried without success.
Reset (soft and hard)
Restore to backup
Then full restore to new phone
Headphone jack in/out 7 or 8 times trick
Blow out headphone jack with compressed air
Carefully cleaning headphone jack with a slightly less cottoned Q Tip
Carefully examined dock port to see if there was debris
Blowing out the dock port with compressed air
Sacrificing a McDonald's chicken nugget to the Gods of hunger
Nothing worked. I've googled the problem and I see that there is a division in the tech nerds between hardware (speaker or dock problem) vs software (Apple screwed up one of the updates). I'm suspecting a dock problem. Phone out of warranty. It's not a brick but it is certainly not as functional as it once was. Any ideas? dock? software? magic? thx.