HTMLPurifier_DefinitionCacheFactory::instance PHP Method

    public static function instance($prototype = null)
    {
        static $instance;
        if ($prototype !== null) {
            $instance = $prototype;
        } elseif ($instance === null || $prototype === true) {
            $instance = new HTMLPurifier_DefinitionCacheFactory();
            $instance->setup();
        }
        return $instance;
    }

 /**
  * Retrieves a definition
  * @param $type Type of definition: HTML, CSS, etc
  * @param $raw  Whether or not definition should be returned raw
  */
 public function getDefinition($type, $raw = false)
 {
     if (!$this->finalized && $this->autoFinalize) {
         $this->finalize();
     }
     $factory = HTMLPurifier_DefinitionCacheFactory::instance();
     $cache = $factory->create($type, $this);
     if (!$raw) {
         // see if we can quickly supply a definition
         if (!empty($this->definitions[$type])) {
             if (!$this->definitions[$type]->setup) {
                 $this->definitions[$type]->setup($this);
                 $cache->set($this->definitions[$type], $this);
             }
             return $this->definitions[$type];
         }
         // memory check missed, try cache
         $this->definitions[$type] = $cache->get($this);
         if ($this->definitions[$type]) {
             // definition in cache, return it
             return $this->definitions[$type];
         }
     } elseif (!empty($this->definitions[$type]) && !$this->definitions[$type]->setup) {
         // raw requested, raw in memory, quick return
         return $this->definitions[$type];
     }
     // quick checks failed, let's create the object
     if ($type == 'HTML') {
         $this->definitions[$type] = new HTMLPurifier_HTMLDefinition();
     } elseif ($type == 'CSS') {
         $this->definitions[$type] = new HTMLPurifier_CSSDefinition();
     } elseif ($type == 'URI') {
         $this->definitions[$type] = new HTMLPurifier_URIDefinition();
     } else {
         throw new HTMLPurifier_Exception("Definition of {$type} type not supported");
     }
     // quick abort if raw
     if ($raw) {
         if (is_null($this->get($type, 'DefinitionID'))) {
             // fatally error out if definition ID not set
             throw new HTMLPurifier_Exception("Cannot retrieve raw version without specifying %{$type}.DefinitionID");
         }
         return $this->definitions[$type];
     }
     // set it up
     $this->definitions[$type]->setup($this);
     // save in cache
     $cache->set($this->definitions[$type], $this);
     return $this->definitions[$type];
 }