array limits in echo function?

I'm just curious: if I use within my html codes: <?php echo $fname $lname; ?>, I get an error message telling me: Parse error: parse error, expecting ','' or ';'' However, if I take out one of the variables so that it reads <?php echo $lname; ?> it works. Has it always been this way? I never noticed before, as I'm quite the newbie. If so, how do I best combine the two (other than having to create two separate <?php..?> codes in the HTML)? Thanks!