title: How to check if mcrypt extension exists in php
body: <p>I would like to know the simplest and fastest PHP code line to check if mcrypt extension is available/installed.</p>
  
  <p>There is a function that encrypts a string and first it requires to check if mcrypt is usable. If not, it will execute an alternative encrypt solution available on the system.</p>
  
  <p>Thanks!</p>