This is what is supplied in 1.11.0 Zend_Filter_StringTrim

    /**
     * Sets filter options
     *
     * @param  string|array|Zend_Config $charList
     * @return void
     */
     public function __construct($charList = null) {
        if ($charList instanceof Zend_Config) {
            $charList = $charList->toArray();
        } else if (!is_array($charList)) {
            $options          = func_get_args();
            $temp['charlist'] = array_shift($options);
            $options          = $temp;
        }

        if (array_key_exists('charlist', $options)) {
            $this->setCharList($options['charlist']);
        }
    }

if an array is given for the constructor parameter the local variable $options is never set and php gives a notice "Undefined variable: options on line 61". In addition, if the typical options array is given to the constructor, the options are never set for the filter. Furthermore if an instance of Zend_Config is supplied as the constructors parameter, it is converted to an array and then disregarded.

I am guessing the constructor was meant to be more like this Updated to reflect Ramon Henrique Ornelas comments and patch

    /**
     * Sets filter options
     *
     * @param  string|array|Zend_Config $options
     * @return void
     */
    public function __construct($options = null)
    {
        if ($options instanceof Zend_Config) {
            $options = $options->toArray();
        } else if (!is_array($options)) {
            $options          = func_get_args();
            $temp['charlist'] = array_shift($options);
            $options          = $temp;
        }

        if (array_key_exists('charlist', $options)) {
            $this->setCharList($options['charlist']);
        }
    }