How to check if mcrypt extension exists in php

Question

I would like to know the simplest and fastest PHP code line to check if mcrypt extension is available/installed.

There is a function that encrypts a string and first it

Answer 1

You can use function_exists to check if one of the mcrypt functions exists.

if(function_exists('mcrypt_encrypt')) {
    echo "mcrypt is loaded!";
} else {
    echo "mcrypt isn't loaded!";
}

Edit 30.07.2016:
Since my answer still gets a few upvotes from time to time, I benchmarked the performance of mine and Cristi Draghici's answers. The conclusion is, that function_exists is a bit faster than extension_loaded. https://3v4l.org/So4Ep