title: Why does it appear that PHP core functions have empty blocks?
body: <p>I'm digging through PHP (using PHPStorm) to figure out how Exceptions work, and I keep running across an interesting situation where functions have empty blocks.</p>
  
  <p>For example, in <code>PHP Runtime/Core/Core.php</code>, the <code>error_reporting</code> function is defined like this:</p>
  
  <pre><code>function error_reporting ($level = null) {}
  </code></pre>
  
  <p>And it's not unique. The top of that files goes like this (ignore all the documentation comments):</p>
  
  <pre><code>&lt;?php
  
  // Start of Core v.5.3.6-13ubuntu3.2
  
  function zend_version () {}
  
  function func_num_args () {}
  
  function func_get_arg ($arg_num) {}
  
  function func_get_args () {}
  
  function strlen ($string) {}
  </code></pre>
  
  <p>Why are the braces all empty? Looking through other core files, I see a lot of function definitions, but no actual code. Where is everything?</p>