They’re both language constructs actually. They don’t require parenthesis, and in fact when using print() in a conditional statement, using parenthesis for the print statement is likely to cause problems.
I agree that it was an unfair characterisation that I made against the print statement. It would be fairer to say that in my opinion, the echo statement is the more useful of the two on a day-to-day basis.
The actual difference between GET and POST is that with GET the browser is allowed to assume that if it does multiple calls passing the same value that the same result will be returned whereas with POST the assumption is that the data on the server may be updated and so a second identical call may return different results.
My favorite part of that post is that at the beginning, they’re printing/echoing “Hello World”, but when they move to concatenation, they completely cut the spaces out of the equation, and are echoing “HelloWorld<br>”.