title: Cannot pass null argument when using type hinting
body: <p>The following code:</p>
  <pre class="lang-php prettyprint-override"><code>class Type {
  
  }
  
  function foo(Type $t) {
  
  }
  
  foo(null);
  </code></pre>
  <p>failed at run time:</p>
  <blockquote>
  <p>PHP Fatal error:  Argument 1 passed to foo() must not be null</p>
  </blockquote>
  <p>Why is it not allowed to pass null just like other languages?</p>