<?php
class FlickrTagElasticaIndexingExtension extends Extension implements ElasticaIndexingHelperInterface {

	/**
	 * Add a mapping for the location of the photograph
	 */
	public static function updateElasticsearchMapping(\Elastica\Type\Mapping $mapping)
    {
    	// get the properties of the individual fields as an array
    	$properties = $mapping->getProperties();

    	// enable tags to be faceted
    	$properties['RawValue'] = array(
    		'type' => 'string',
    		'index' => 'not_analyzed'
		);

    	// set the new properties on the mapping
    	$mapping->setProperties($properties);

        return $mapping;
    }


	/**
	 * Populate elastica with the location of the photograph
	 * @param  \Elastica\Document $document Representation of an Elastic Search document
	 * @return \Elastica\Document modified version of the document
	 */
	public function updateElasticsearchDocument(\Elastica\Document $document)
	{
		// No alterations made, so just pass through the document
	    return $document;
	}
}

<?php
class FlickrTagElasticaIndexingExtension extends Extension implements ElasticaIndexingHelperInterface {

	/**
	 * Add a mapping for the location of the photograph
	 */
	public function updateElasticsearchMapping(\Elastica\Type\Mapping $mapping)
    {
    	// get the properties of the individual fields as an array
    	$properties = $mapping->getProperties();

    	// enable tags to be faceted
    	$properties['RawValue'] = array(
    		'type' => 'string',
    		'index' => 'not_analyzed'
		);

    	// set the new properties on the mapping
    	$mapping->setProperties($properties);

        return $mapping;
    }


	/**
	 * Populate elastica with the location of the photograph
	 * @param  \Elastica\Document $document Representation of an Elastic Search document
	 * @return \Elastica\Document modified version of the document
	 */
	public function updateElasticsearchDocument(\Elastica\Document $document)
	{
		// No alterations made, so just pass through the document
	    return $document;
	}


	public function updateElasticHTMLFields(array $htmlFields) {
		return $htmlFields;
	}
}

Change of interface, removing the static method
FIX: Change of interface, removing the static method
