<?php
/** 
 * !RespondsWith Layouts, Json 
 * !Prefix my/
 **/
class MyController {
    /** !Route GET, hello/ */
    function hello() { return $this->ok('hello'); }
}
?>

<?php
$title = "Hello World?";
include('print-heading.php');
echo $title;
?>
===
<?php // print-heading.php
echo "<h1>$title</h1>\n";
unset($title);
?>
===
Output:
<h1>Hello World</h1>
Notice: Undefined variable: title

<?php // print-heading.part.php
Part::input($title, 'string'); 
Part::input($level, 'int');

/////// Presentation Logic //////
echo "<h$level>$h1</h$level>\n";
unset($title);
?>

<?php
$title = "Hello world?";
Part::draw('print-heading', $title, 1);
echo $title;
?>
===
Output:
<h1>Hello world?</h1>
Hello world?

Note that even though print-heading.part.php unsets $title, it has no effect on our top-level template. Also note that, with the way drawing the Part does not require knowing the names of the variables within print-heading.part.php. We simply just have to pass the right number of variables in. If this feels more like a function than an include, you're right, it's a lot like a function with typed inputs.

We'll go into more depth in the section describing the class AssertiveTemplate, the common superclass of Layouts & Parts. Although there is additional effort in defining input, it simplifies your reasoning about view logic and makes working with templates (especially other people's!) much more predictable.