Kirki_Styles_Output_CSS::css PHP Method

        public static function css($field)
        {
            // Set class vars.
            self::$settings = $field['settings'];
            self::$callback = $field['sanitize_callback'];
            self::$field_type = $field['type'];
            self::$output = $field['output'];
            if (!is_array(self::$output)) {
                self::$output = array(array('element' => self::$output, 'sanitize_callback' => null));
            }
            // Get the value of this field.
            self::$value = Kirki_Values::get_sanitized_field_value($field);
            // Find the class that will handle the outpout for this field.
            $classname = 'Kirki_Output';
            $field_output_classes = apply_filters('kirki/' . $field['kirki_config'] . '/output/control-classnames', array('kirki-spacing' => 'Kirki_Output_Field_Spacing', 'kirki-typography' => 'Kirki_Output_Field_Typography', 'kirki-multicolor' => 'Kirki_Output_Field_Multicolor'));
            if (array_key_exists(self::$field_type, $field_output_classes)) {
                $classname = $field_output_classes[self::$field_type];
            }
            $obj = new $classname($field['kirki_config'], self::$output, self::$value);
            return $obj->get_styles();
        }

 /**
  * loop through all fields and create an array of style definitions
  */
 public static function loop_controls()
 {
     // Get an instance of the Kirki_Styles_Output_CSS class.
     // This will make sure google fonts and backup fonts are loaded.
     Kirki_Styles_Output_CSS::get_instance();
     $fields = Kirki::$fields;
     $css = array();
     // Early exit if no fields are found.
     if (empty($fields)) {
         return;
     }
     foreach ($fields as $field) {
         // Only continue if $field['output'] is set
         if (isset($field['output']) && !empty($field['output']) && 'background' != $field['type']) {
             if (function_exists('array_replace_recursive')) {
                 $css = array_replace_recursive($css, Kirki_Styles_Output_CSS::css($field));
             } else {
                 $css = Kirki_Helper::array_replace_recursive($css, Kirki_Styles_Output_CSS::css($field));
             }
         }
     }
     if (is_array($css)) {
         return Kirki_Styles_Output_CSS::styles_parse(Kirki_Styles_Output_CSS::add_prefixes($css));
     }
     return;
 }