How do I check if a given PHP extension is available?

PHP has a built-in function that outputs a web page with all of PHP’s loaded configuration: phpinfo().

To find out if a given PHP extension is loaded or other configuration directives, you can create a new file inside your public_html with the following contents:

<?php phpinfo(); ?>

For example, lets say I saved the file in public_html/info.php, so I should now be able to browse http://mysite.com/info.php (remember to replace mysite.com with your actual domain name).

The page output will include information about the version of PHP being used, loaded extensions, and a lot more.