title: when does php json_decode return false?
body: <p>In the PHP documentation for <a href="http://php.net/manual/en/function.json-decode.php"><code>json_decode</code></a> it says it can return <code>TRUE</code>,<code>FALSE</code>,<code>NULL</code>.</p>
  
  <p>Could some help me understand when it would return <code>FALSE</code>? I understand invalid JSON will return <code>NULL</code>, but when would the other two be returned if not the actual JSON value?</p>
  
  <p>Thanks</p>