Example code to extend Timber/Twig with custom filters and functions

toolbox-Twig-Extend.php

<?php

class toolboxTwigExtend {
  
    public static function init() {

        add_filter( 'timber/twig', __CLASS__ . '::add_to_twig' );
    }

    public static function add_to_twig( $twig ) {
	    /* this is where you can add your own functions to twig */
	    $twig->addExtension(new Twig_Extension_StringLoader());

	    /**
	     * Template filter for Twig
	     * @usage  {{var|whatever(4)}}
	     */
	    $twig->addFilter(new Twig_SimpleFilter( 'whatever', __CLASS__ . '::my_whatever'  ) );

	    /**
	     * Dump variable
	     * @usage  {{ dumpv( var ) }}
	     */
	    $twig->addFunction(new Timber\Twig_Function( 'dumpv', __CLASS__ . '::dump'  ) );

	    /**
	     * Get multiple acf field values
	     * @usage {% set myfields = get_multi_fields( [ 'field1', 'field2' ] ) %}
	     */
	    $twig->addFunction(new Timber\Twig_Function( 'get_multi_fields', __CLASS__ . '::get_fields'  ) );

	    return $twig;
    }

    /**
     * Example Filter for Twig
     * @param  [type]  $text   [description]
     * @param  integer $repeat [description]
     * @return [type]          [description]
     */
    public static function my_whatever( $text , $repeat = 1 ) {

    	for ( $i = 0; $i < $repeat; $i++ ) {

    		$text .= ' or whatever';

    	}

	    return $text;
	}

	/**
	 * Example Function for Twig
	 * @param  [type] $var [description]
	 * @return [type]      [description]
	 */
    public static function dump( $var ) {

    	ob_start();

    	var_dump( $var );

    	return ob_get_clean();
    }

    /**
     * Get a bunch of fields for reuse.
     * @param  array   $fieldnames [description]
     * @param  integer $postid     [description]
     * @return [type]              [description]
     */
    public static function get_fields( $fieldnames = array() , $postid = 0 ) {
    	
    	if ( is_array( $fieldnames ) && sizeof( $fieldnames ) > 0 ) {

    		foreach ( $fieldnames as $field ) {

    			$return[ "{$field}" ] = get_field( $field , $postid );

    		}

    	} else if( is_string( $fieldnames ) && $fieldnames !== '' ){

			$return[ "{$fieldnames}" ] = get_field( $fieldnames , $postid );

    	}

		return $return;
    }
}

toolboxTwigExtend::init();