So all $1 phone chargers are safe and it's the iPhone that doesn't work with them?
Considering that Apple has built in a detection mechanism to prevent the iPhone from working with any cable that isn't properly licensed and authorized by Apple, then yes it is the phones fault. Or Apple's fault. You pick.
There is a chip in the cable, that Apple uses to establish if said cable is authorized to be used with the phone.
But blaming a cable for a burning phone is like blaming the extension cord for the Toaster catching on fire.
If the extension cord catches on fire and the fire spreads to the toaster, then blame the cord.
If the toaster catches on fire internally, and the extension cord is unharmed, then blame the toaster.
Or... we could go a different route... let's blame the house. After all, the house should have known the phone was fully charged and turned off the electricity on that wall outlet.
Now, you could potentially blame the charger (not the cable) if the charger failed to properly regulate the power sent through to the cable. The charger is a converter. It converts 110 or 220 volts AC to approximately 5 volts DC.
The charger then sends that DC power through the cable to the phone.
Now, a good circuit design will measure incoming power, and determine if it is within acceptable limits. A mechanism I would hope the iPhone is using.
But, suppose the charger suddenly sends 20 volts through the cable due to a malfunction. In typical cases, the cable will melt if it's not rated for 20 volts. Thus the cable will burn first.
If this were to happen, and the cable didn't melt, then here's where another piece of ancient technology comes into place. All electronic devices of quality design, should have a sacrificial element that will break first, and sever the supply of power to the device to prevent fire caused by overcurrent. Those of us that have been around a bit, call these sacrificial elements "fuses".
Obviously, technology is now smaller than a traditional fuse. But the same effect is achieved by having a trace wire inside the device that is slightly weaker than the rest of the devices internal circuitry.
This weaker link should be placed very close to the supply of power entering the device (phone in this circumstance). That way if the supply of power does become greater than is safe, the weak link breaks, power is fully cut off to the devices other parts. And all that happens is the device doesn't work anymore.
Now, if ancient technology like fuses is beyond Apple's level of comprehension, then it's time they get out of the electronics industry.
So, to sum it up, if the smoke, fire, sparks, etc originate inside the device, then the device (or its design team) is to blame. If the cord burns first and the flames spread to the phone, then blame the cord.
By blaming the cable for a fire that originated inside the phone, essentially you're saying Apple couldn't even grasp the concept of how a lightbulb works. If this is your defense of Apple, I'd seriously consider buying from someone else.