In PHP, why wasn't echo implemented as a function? (not echo vs. printf)

[Exculuccexins]

I'm just curious. In PHP, why wasn't \[code\]echo\[/code\] implemented as a function? Why didn't PHP just give us \[code\]printf\[/code\] and never tell about \[code\]echo\[/code\]? Please note that:

• This is not a question about \[code\]echo\[/code\] vs. \[code\]printf\[/code\].
• I already knew that \[code\]echo\[/code\] is a language construct.

UPDATE: By the way, was \[code\]printf\[/code\] implemented using \[code\]echo\[/code\]?