[delta7]

Can I use this charger with my m7? If not I need a authentic charger and I'm scared of ebay fakes.

[IAmSixNine]

Yes you can use your Samsung GS4 charger to charge the M7.

[IAmSixNine]

First you have to match the 1A or 2A and also output voltage then you can rely that s4 charger. I am also recommending you a car charger which is multi-purpose car charger. It have different types of output voltage and it is very reliable charger and best for all your devices. I found this device on Amazon, Please take a look:
Amazon.com: AVANTEK 7.8A / 39W Output 5-Port Intelligent USB Car Charger Charging Station for Cell Phones, iPhones, iPads, Tablet Computers, MP3 Players & GPS's: Cell Phones & Accessories

roger_2014 your post is incorrect. You do NOT need to match the current output for a specific device unless the device requires a minimum current input to operate.
For example, you can use a 2A charger on any device. The device its self has current limiting hardware / software to prevent it from damage.
However, some tablets, (think iPad) require 1.5-2A before it will recognize it as a proper charger. Using a 1A charger on an iPad will in some cases show "Not Charging" next to the battery symbol.
Micro USB is an industry standard and should always be 5 volts. (5.1 to 4.9 is acceptable)
Also if you notice the car charger you recommend for him does NOT have different types of output voltage as you suggest. They are all 5 volts. IT does however have different max current outputs. Those are all variable. What they are showing is the max current output per slot, so they can go lower then that as necessary. The device will control how much current goes into it with the max being limited by either the device or the charger. If a device requires more then 2 amps then the charger is the limit.
I have an identical home charger from a company called Inateck that works great.
Inateck UC5001 5-Port 35W USB Family-Sized Desktop Charger
Its been a very good charger.