public function hyphen_to_camel( $string, $upper_first = false ) {
		$str = preg_replace_callback( '/-(.)/u', function ( $match ) {
			return strtoupper( $match[1] );
		}, strtolower( $string ) );
		if ( $upper_first ) {
			$str = ucfirst( $str );
		}

		return $str;
	}