Opening tags and basic output

PHP code lives inside tags so the server knows what to execute versus what to send as plain HTML. The modern standard is <?php ... ?>; short tags <?= echo shorthand are common in templates.

Standard opening tag

<?php
echo "Hello, world!\n";
?>

Every statement ends with a semicolon. Omitting it causes a parse error on the next line.

Mixing PHP and HTML

<?php $name = 'Ada'; ?>
<p>Hello, <?= htmlspecialchars($name) ?></p>

In real templates, always escape output with htmlspecialchars (or a template engine) to prevent XSS.

CLI vs web SAPI

The same syntax runs in the browser context (via a web server) and on the command line (php script.php). This playground uses the CLI-style runner—no HTML wrapper required unless you echo it.

Important interview questions and answers

1. Q: Why use full <?php tags?
   A: Portability—short tags may be disabled in php.ini; full tags work everywhere.
2. Q: What is <?=?
   A: Short echo tag, equivalent to <?php echo ... ?> when enabled.

Self-check

1. What punctuation ends a PHP statement?
2. Why escape user data before echoing into HTML?

Tip: Always use full <?php tags in portable code—short tags may be disabled in production php.ini.