Creating functions without parentheses in PHP like 'echo'

There simply isn't. "echo" is more of an operator than a function, so you'd actually need to rewrite the PHP interpreter source in order to introduce new "functions" like those.

Edit: Actually, the more accurate term for "echo" is, as eyze has correctly pointed out, language construct rather than operator. http://php.net/manual/de/function.echo.php provides some more information.

Simple answer, no.

echo is a language construct not a function, hence it doesn't need the parentheses.