Status : 404 Not Found

Absolutely, it's just a matter of figuring out the right PHP code and exactly what you want to do.

If you see if you blog.php code the part that shows the 404:

// error if page not found
if (!$pageRecord) {
header("HTTP/1.1 404 Not Found");
...

That basically says, if we can't find a page, show the 404. We can add a line that checks if there is a / on the end of the url and show the 404 if there is no page -OR- if there is no slash on the end. Like this:

// error if page not found
$urlEndsWithSlash = preg_match("|/$|", @$_SERVER["PATH_INFO"]);
if (!$pageRecord || !$urlEndsWithSlash) {
header("HTTP/1.1 404 Not Found");
...

That will show the 404 for: /blog.php/page2 and also /blog.php since there is no slash on the end. You'd have to use /blog.php/.

If you want a 404 on any page without a slash EXCEPT "/blog.php" then you could use this:

// error if page not found
$urlEndsWithSlash = preg_match("|/$|", @$_SERVER["PATH_INFO"]);
$pageNameSetAndNoSlash = (@$_SERVER["PATH_INFO"] && !$urlEndsWithSlash);
if (!$pageRecord || $pageNameSetAndNoSlash) {
header("HTTP/1.1 404 Not Found");
...

The PHP preg_match() function used "regular expressions" to see if something matches a pattern. In this case, to see if the url ends in a slash. Anyway, hope that helps! :)