title: Performance of storing global constants in a class
body: <p>I've recently started using  classes in my projects, and one of the uses is to set and store global constants in a <code>private</code> array. I'm wondering if this is common practice, bad and, most importantly, slow if I'm doing lots of calls to the fetch function in the class (lots as in, whenever I need the site name, an email address or MySQL details).</p>
  
  <p>I'm not posting the code because it's really basic; just a function that <code>returns</code> the value of an item in the array with the key given.</p>