<?php
echo "Hello World";
?>
<br />
<?php
echo "Welcome";
?>

<?php
echo "Hello World";
echo "<br />";
echo "Welcome";
?>

<?php
include 'header.html';
...
include 'footer.html';
?>

<?php echo "<p>Hello World</p>"; // Alway wrong. ?>

<p>Hello World</p>  <!-- Does the same thing, faster, and is more readable. -->

if ($something) {
  do_something(); // do_something() shouldn't echo or print.
}

<?php
  if ($something) {
    echo '<p>Hello World.</p>';
  }
?>

<?php if ($something) { ?>
  <p>Hello World.</p>
<?php } ?>

<?php if ($something): ?>
  <p>Hello world.</p>
<?php endif; ?>

<?php foreach ($things as $thing): ?>
  <li><?php echo $thing; ?></li>
<?php endforeach; ?>

<li><?php echo $thing; ?></li>

<li><?=$thing?></li>

<li>{thing}</li>

<?php echo "Hello World"; ?>
<br />
<?php echo "Welcome"; ?>

echo "Hello World";
echo "<br />";
echo "Welcome";

<?php echo "Hello World<br>Welcome"; ?>