title: OOP PHP extended class multiple includes
body: <p>I am learning OOP techniques, so please don't be too harsh if my question sounds too basic ^_^
  I have 4 php files.</p>
  
  <pre><code>index.php
  parentClass.php
  childClass1.php
  childClass2.php
  </code></pre>
  
  <p>childClass1.php and childClass2.php basically extend the parentClass.php. So my question is does the index.php file call the parentClass twice if I include or require both child classes in the index file? For example something like:</p>
  
  <pre><code>require_once("childClass1.php");
  $child1 = new childClass1();
  require_once("childClass2.php");
  $child2 = new childClass2();
  </code></pre>