使用括号时，打印构造的行为是否有所不同？

Question

I am not sure if parentheses make difference or I am doing something wrong! Here is a situation I accidentally encountered..

 print (FALSE or TRUE);     //prints '1'
 print FALSE or TRUE;       //prints nothing

We know that FALSE or TRUE evaluates to TRUE, but surprisingly, printing TRUE is not affected by parentheses!

  print (TRUE);     //prints '1'
  print TRUE;       //prints '1'

The manual mentions clearly that using parentheses is not required! Here is a quote from the manual..

print is not actually a real function (it is a language construct) so you are not required to use parentheses with its argument list.

What I want to know ..

• Is it a bug?
• If it is not a bug, how do parentheses affect the output?
• Which way gives expected output, using parentheses or omitting them?

I am using PHP Version 5.4.7 on Windows 8.

Thanks!

Answer 1

print (FALSE or TRUE);     //prints '1'

evaluates FALSE or TRUE (which gives TRUE), and then prints the result of that evaluation

print FALSE or TRUE;       //prints nothing

prints FALSE (which is displayed as an empty string); and if that fails (or) then does nothing with TRUE