PHP echo变量和html结合在一起

Question

I know this is a basic php question, but I'm having trouble showing variables inside an echo of HTML. Below is what I'm trying to achieve.

<?php
    $variable = 'testing';
    echo <span class="label-[variable]">[variable]</span>
?>

should output:

<span class="label-testing">testing</span>

Answer 1

<?php
    $variable = 'testing';
    echo <span class="label-[variable]">[variable]</span>
?>

Should be

<?php
    $variable = 'testing';
    echo '<span class="label-' . $variable .'">' . $variable . '</span>';
?>