How to transfer all contacts, music, photos to another iphone?

So me and my mom both have the iphone 4 n we want to switch so I'm wondering how to transfer all of my stuff into her iphone n her stuff to my iphone

Connect your phone to iTunes, make sure your purchases have been transferred to the computer, and then back up your phone to the computer. After that is complete, repeat that with the other phone. Then go on the phone. Go into settings>general>(Scroll to bottom)>reset>Erase all content as settings. Then once that's finished, restart the phone and set it up again. Make sure when setting it up, choose "set up a old (or previous) iPhone." Then connect to iTunes and set up as the other phone. Repeat the process with the other phone, and they will be switched.
Also. Make sure to switch the SIM cards out; otherwise you will switch numbers

Make sure both phones are the same disk size. (32gb for 32gb) If not complications will arise if one phone has more memory than the other)

If you have a computer for each phone it will make it easier. I'm going to assume you have one computer with iTunes and 2 phones.

Plug both phones into the computer. Right click on each device and create backup for each device.

Once that is done, select eject for device A and unplug it. Now with device B, select restore, and restore from backup A. (This will take 30mins to 2 hrs)

Now once that's done, eject and unplug device B. Plug in device A and select restore from backup of backup B. (This will take 30mins to 2 hrs)

Once that's done, you have completed the restore.

The easiest way would be to do a manual backup into iTunes through a computer. Make sure to turn off automatic syncing first. But that's just for personal content. Music will not be saved. You would have to re-download it from the purchase history in your iTunes store account or re-import it from where you got it in the first place.

Step 1: Install iPhone Transfer Platinum
Step 2: Connect your iPhone
Step 3: Transfer various iPhone files to Another

On the left side of the main interface, you will see the display list, which will show your various iPhone files in different types. You can freely choose any kind of file type(music, movie, TV shows, Podcast, iTunes U, Ringtones, Books, pictures/Cameare Roll, Voice Memo, Camera Shot, SMS and Contacts) to transfer to your PC for file safety or other use.

Here, take transferring songs to anther iPhone for example.

Click "Music" on the display list, then the right side of the interface will display all your music files in details as the following screenshot shows.
In front of each listed music file, there's a check box, you can check all to choose all music files or just one to choose, then click "Device to Device" image button on the bottom of the interface to start transferring music files from iPhone to anther.

Source: http://www.video-dvd-ripper.com/iphone-transfer/