Fatal error: Call to undefined function random_bytes()
<p>I'm using php 5.6.23-0+deb8u1 and in my code I want use the function <code>random_bytes</code> but I get this error:</p>

<blockquote>
  <p>Fatal error: Call to undefined function random_bytes() </p>
</blockquote>

<p>I want to know if I need to import something or isn't included in this version of php, in this case, how can I replace it?</p>