echo's "here document" syntax

Dear list, I was looking through the documentation of PHP and I came across this in ECHO's page echo <<<END This uses the "here document" syntax to output multiple lines with $variable interpolation. Note that the here document terminator must appear on a line with just a semicolon no extra whitespace! END; I tried this out in my scripts and it works great! I've never been a fan of smarty or templates in general, and this seems to be right up my alley as a not-quite-as-good but better-than-nothing substitute. Does anybody know the history of this method? "here document" wha? Where'd it come from? What are its shortfalls? Is it significantly slower than the echo " [huge block of text with php vars] "; method? Thanks, Micah