title: Get the number of time a class method has been invoked?
body: <p>Let's say I have this class.</p>
  
  <pre><code>class foo{
    function a(){
       return $this; 
    }
  }
  </code></pre>
  
  <p>And I instantiate it as: </p>
  
  <pre><code>$O = new foo(); 
  $O-&gt;a()
    -&gt;a()
    -&gt;a();
  </code></pre>
  
  <p>Is there any way to know, in that last function <code>-&gt;a()</code> how many times it was called before? 
  So, I could output like <code>'method -&gt;a() has been called twice before this.'</code> 
  I would like to find out this, without using increment values like declaring a property and then increment it increment it, everytime it is called in a function. </p>
  
  <p>I am just hopping if there is a hidden feature in OOP that can provide for this solution</p>