title: What's the execution flow of below PHP scripts?
body: <p>I have a test.php:</p>
  
  <pre><code>&lt;?php
  
  include "MyString.php";
  
  print ",";
  print strlen("Hello world!");  
  </code></pre>
  
  <p>and a MyString.php:</p>
  
  <pre><code>&lt;?php
  
  namespace MyFramework\String;
  
  function strlen($str)
  {
      return \strlen($str)*2; // return double the string length
  }
  print strlen("Hello world!");
  </code></pre>
  
  <p>The output of test.php is 24,12 but how was the output produced? What are the execution flow of test.php?</p>
  
  <p>Also there is a back slash in:</p>
  
  <pre><code>namespace MyFramework\String;
  
  function strlen($str)
  {
      return \strlen($str)*2; // return double the string length
  }
  </code></pre>
  
  <p>Is this '\' means using namespace?</p>