phpinfo() and PHP version

Learn the server configuration with phpinfo() and the PHP_VERSION constant.

What is phpinfo()?

phpinfo() is a built-in function that displays PHP configuration information. It produces a detailed table about the version, extensions and server settings.

It is simple to use: <?php phpinfo(); ?> — write this in a file and open it on the server to see the info table.

During development it is very useful for checking which extensions are installed.

Security note: do not leave a phpinfo() page publicly accessible on a live site; it leaks server information.

The PHP_VERSION constant

PHP_VERSION is a built-in constant that holds the installed PHP version. Its value is a string like "8.3.0".

Usage: echo PHP_VERSION; — this prints the version number.

Similar constants exist: PHP_SAPI gives the server interface type (for example cli or apache2handler).

Constants are written in uppercase and do not take a $ sign.

Exercise phpinfo comment and print version

Write a PHP block. Include the word phpinfo() in a // comment. Then use echo to print "PHP 8.3"; add \n at the end of the line.

Show example solution

Write phpinfo in a // comment, then add echo "PHP 8.3\n";.
Example solution:
<?php
// phpinfo() gives configuration info
echo "PHP 8.3\n";

Test yourself

What does phpinfo() show?
- The browser version
- PHP errors
- Database records
- PHP configuration info
Show answer

PHP configuration info — Correct! phpinfo() shows PHP configuration info.
Match the PHP constants

phpinfo()

Configuration info
PHP_VERSION

Version number
PHP_SAPI

Server interface

Write the version constant

<?php echo ____; ?>

Show answer

<?php echo PHP_VERSION; ?>

Next lesson: Summary - PHP basics

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