Automatically clear captured placeholder view-helper content after it is displayed

Question

Generating a mail message in a partial, I use the placeholder view-helper as follows:

<?php $this->placeholder('mykey')->startCapture() ?>
    Some content here that is actually more complicated than just text. 
    Trust me that, in this case the, using the placeholder for capturing 
    is desirable.
<?php 
    $this->placeholder('mykey')->endCapture();
    echo $this->placeholder('mykey');
 ?>

The problem is that if I use the same key in a different partial for a different mail message within the same request, then this captured content is still stored in the container for that key. In principle, I'd like the partials to be free to use whatever placeholder keys they want without having to sweat what other partials are using.

I know I can use different keys in different partials. Alternatively, I can manually clear the content after use/display with something like:

$this->placeholder('mykey')->set('');

But I'd hate to put the burden of all that on the view script that uses the placeholder.

I suspect what I want to do is create my own custom placeholder view-helper that auto-clears his captured content after it has been output.

I've tried creating a custom placeholder container (extends the Standalone container, overriding the toString() method), creating a custom view-helper (extends the the standard Placeholder view-helper), and telling the view-helper to use the custom container class.

But I keep bumping into some error associated to a missing view object. Clearly, I'm missing something about the how the view object, the container, and the registry all interact - and probably even something how the plugin system loads them all.

Any advice and general explanation greatly appreciated.

Answer 1

You need to set this container in the Placeholder view helper because otherwise the Zend_View_Helper_Placeholder_Registry loads automatically the Zend_View_Helper_Placeholder_Container. So, first you need to set your custom container manually. In a view script:

$this->getHelper('placeholder')
     ->getRegistry()
     ->setContainerClass('My_View_Helper_Placeholder_Container');

Or for exameple in a _initCustomContainer() in your Bootstrap.php:

$view = $this->bootstrap('view')->getResource('view');
$view->getHelper('placeholder')
     ->getRegistry()
     ->setContainerClass('My_View_Helper_Placeholder_Container');

Then, you need to create this class based on the Zend_View_Helper_Placeholder_Container (and not the Zend_View_Helper_Placeholder_Container_Standalone. I'd suggest you keep the option open to reset the content or not, you do that with a setter:

class My_View_Helper_Placeholder_Container
    extends Zend_View_Helper_Placeholder_Container
{
    protected $_resetCapture = true; // defaults true for new behaviour

    public function setResetCapture($flag)
    {
        $this->_resetCapture = (bool) $flag;
        return $this;
    }

    public function toString($indent = null)
    {
        $return = parent::toString($indent);

        if ($this->_resetCapture) {
            $this->exchangeArray(array());
        }

        return $return;
    }
}

By default, the reset capture is already on, but to switch it off and start capturing:

$this->placeholder('my_key')->setResetCapture(false)->startCapture();

And to switch it on again:

$this->placeholder('my_key')->setResetCapture(true);