Fixing a weird problem with PHP 5.6.1

I am getting errors when using ifelse on EE 2.9.2  with PHP 5.6.1:

<h4>A PHP Error was encountered</h4>

<p>Severity: 8192</p>
<p>Message:  Non-static method Ifelse::usage() should not be called statically, assuming $this from incompatible context</p>
<p>Filename: ifelse/pi.ifelse.php</p>
<p>Line Number: 10</p>

This type of fix was proposed here.
http://stackoverflow.com/questions/21437371/strict-standards-non-static-method-assuming-this-from-incompatible-context

Am I doing it correctly?