Caching#

Object caching#

Any values accessed from a template on a ModelData object are cached after first access. Because of this, methods that provide data to templates should ideally have no side effects. For example, this getCounter() method will not behave as you might imagine when invoked from a template.

namespace App\Model;

use SilverStripe\ORM\DataObject;

class MyObject extends DataObject
{
    // ...

    private $counter = 0;

    public function getCounter()
    {
        $this->counter += 1;

        return $this->counter;
    }
}

$Counter, $Counter, $Counter
// renders as 1, 1, 1

When we render $Counter to the template we would expect the value to increase and output 1, 2, 3. However, as $Counter is cached at the first access, the value of 1 is used each time it is invoked in this template.

Partial caching#

Partial caching is a feature that allows caching of a portion of a page as a single string value. For more details read its own documentation.

Example:

<% cached $CacheKey if $CacheCondition %>
    $CacheableContent
<% end_cached %>

Template caching#

Every time a raw template file is processed, some PHP code is generated from it which is then executed to produce the final rendered result.

That PHP code is cached in the filesystem so that the raw template file doesn't need to be processed again until either the cache is flushed or the raw template file is updated.