Question

Both are working fine. I’m just curious how php parse the two. Do they have difference on speed, efficiency, etc. Why does php allow us to use both?

Answer 1

if you are using just literal php recognizes this as a constant. So it try to find that constant, and if it fails – it just assumes that your desire was using string literal 'literal'. But, to indicate that it doesn’t found the constant it raises Notice level error.

So, using just literal have tweo drawbacks:

1. If you have constant literal defined – you’ll get it’s value (and this is a correct usage), not string 'literal'
2. You’ll receive a Notice if you don’t have such constant.

So, don’t use just literal unless you have a constant with that name defined.