framework/helpers/BaseHtml.php
public static function removeCssClass(&$options, $class)
    {
        if (isset($options['class'])) {
            if (is_array($options['class'])) {
                $classes = array_diff($options['class'], (array) $class);
                if (empty($classes)) {
                    unset($options['class']);
                } else {
                    $options['class'] = $classes;
                }
            } else {
                $classes = preg_split('/\s+/', $options['class'], -1, PREG_SPLIT_NO_EMPTY);
                $classes = array_diff($classes, (array) $class);
                if (empty($classes)) {
                    unset($options['class']);
                } else {
                    $options['class'] = implode(' ', $classes);
                }
            }
        }
    }
public static function removeCssClass(&$options, $class)
    {
        if (isset($options['class'])) {
            if (is_array($options['class'])) {
                $classes = array_diff($options['class'], (array) $class);
                if (empty($classes)) {
                    unset($options['class']);
                } else {
                    $options['class'] = $classes;
                }
            } else {
                $classes = preg_split('/\s+/', $options['class'], -1, PREG_SPLIT_NO_EMPTY);
                $classes = array_diff($classes, (array) $class);
                if (empty($classes)) {
                    unset($options['class']);
                } else {
                    $options['class'] = implode(' ', $classes);
                }
            }
        }
    }
Removes a CSS class from the specified options.
@param array $options the options to be modified.
@param string|array $class the CSS class(es) to be removed
@see addCssClass()