echo two variables on the one line

Hi, i have a page that echoes my username at the top of the page, however i want to change it to [B]firstname[/B] [B]lastname[/B]

At the top of the page the following code appears:

<? echo $_SESSION[‘user_info’][‘username’];?>

however my firstname and lastname are the following variables. How do output the two of these with just the one echo

firstname = [B]$_SESSION[‘my_array’][1][/B]
lastname = [B]$_SESSION[‘my_array’][12][/B]

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