code: protected static function unify_files( $params, $data = '' ) {
  
  		$type      = $params['type'];
  		$routes    = $params['routes'];
  		$extension = ( 'style' == $type ) ? '.css' : '.js';
  		$hash      = sha1( implode( '', $params['files'] ) );
  		$min_file  = $routes['path'] . $hash . $extension;
  
  		if ( ! is_file( $min_file ) || self::$changes ) {
  			foreach ( $params['paths'] as $id => $path ) {
  				if ( isset( $params['urls'][ $id ] ) ) {
  					$url   = $params['urls'][ $id ];
  					$path  = $routes['path'] . $params['files'][ $id ];
  					$data .= self::save_external_file( $url, $path );
  				}
  
  				$data .= file_get_contents( $path );
  			}
  
  			$data = ( self::$minify ) ? self::compress_files( $data ) : $data;
  
  			self::save_file( $min_file, $data );
  		}
  
  		self::set_processed_files();
  
  		return self::set_new_params( $type, $hash, $routes['url'], $extension );
  	}
docs: Unify files.
  
  @since 1.0.4
  
  @param array  $params → paths and urls of files to unify.
  @param string $data   → initial string.
  
  @return boolean true