How $this works in .phtml files in zend framework?

问题:

For all my practice with OOP I have never used $this outside of the class definition.

While in zendframework we use $this in view template files, obviously it is not the scope of a class definition. I wonder how it has been implemented ? I have googled a lot but got no luck.

I want to know the mechanism how zendframework renders it's view files with $this.

回答1:

It actually is in the scope of a class definition. Simple test-case:

<?php
// let's call this view.php
class View {
   private $variable = 'value';
   public function render( ) {
       ob_start( );
       include 'my-view.php';
       $content = ob_get_clean( );
       return $content;
   }
}
$view = new View;
echo $view->render( );

Now, create another file:

<?php
// let's call this my-view.php.
<h1>Private variable: <?php echo $this->variable; ?></h1>

Now go and visit view.php, and you will see that my-view.php had access to the private variable of the View class. By using include, you actually load the PHP file into the current scope.

回答2:

In view script files (.phtml ones) $this refers to the currently used instance of Zend_View class - the one that is ordered to render this particular script. Quoting the doc:

This is [a view script] a PHP script like any other, with one exception: it executes inside the scope of the Zend_View instance, which means that references to $this point to the Zend_View instance properties and methods. (Variables assigned to the instance by the controller are public properties of the Zend_View instance).

And this it how it's done: when your controller calls (explicitly or implicitly) render method (defined in Zend_View_Abstract class), the following method (defined in Zend_View class) is executed in the end:

/**
 * Includes the view script in a scope with only public $this variables.
 *
 * @param string The view script to execute.
 */
protected function _run()
{
   if ($this->_useViewStream && $this->useStreamWrapper()) {
      include 'zend.view://' . func_get_arg(0);
   } else {
      include func_get_arg(0);
   }
}

... where func_get_arg(0) refers to the full filename (path + name) of the included script.