PHP Tags

PHP code lives inside tags. Anything outside the tags is sent to the browser unchanged. Anything inside is run as PHP.

The opening and closing tags

1
2
3
4
5

<p>This is plain HTML.</p>
<?php
echo "<p>This line was written by PHP.</p>\n";
?>
<p>Back to plain HTML.</p>

1
2
3

<p>This is plain HTML.</p>
<p>This line was written by PHP.</p>
<p>Back to plain HTML.</p>

<?php starts PHP mode. ?> ends it. You can switch between HTML and PHP as many times as you like in one file.

The short echo tag

When you only want to print one value, <?= is a short way to write <?php echo.

1
2

<?php $city = "Mumbai"; ?>
<p>Weather in <?= $city ?></p>

1

<p>Weather in Mumbai</p>

The short echo tag is always available. It is common in templates.

Files that contain only PHP

If a file contains only PHP, leave out the closing ?> tag. The standard coding style does the same, and it avoids a classic bug.

1
2
3

<?php
// config.php: nothing but PHP, so no closing tag
$siteName = "My Blog";

Why? Any space or blank line after ?> is sent to the browser as output. That stray output can break features that must happen before any output, such as redirects and cookies.

Tags you should not use

• <? (the short open tag) depends on a setting that is often off. Do not use it.
• <script language="php"> and <% %> were removed long ago.