is_single() works in plugin, not in theme?

Question

I'm attempting to move some code from a plugin over to my theme's functions.php file, but when I attempt to wrap it in the is_single() wrapper inside of functions.php, it never fires. What am I missing?

if (is_single()) {
echo "hello world"; 
}

I can't get the echo to fire from any inside post page.

This has to be something insanely simple I'm overlooking.

Answer 1

All that I can think of is to verify that you are in fact on a single post page ( echo out an else conditional, make sure that you are actually hitting your block of code ).

if ( is_single() ) {
    echo 'Hello World, Is Single';
} else {
    echo 'Not Single';
}

Where exactly are you placing the code (Header, Body, Footer, which template file)? Are you using any frameworks like Carrington ?