Method test

/**
 * Method to test the value.
 *
 * @param   \SimpleXMLElement  $element  The SimpleXMLElement object representing the `<field>` tag for the form field object.
 * @param   mixed              $value    The value to validate.
 * @param   string             $group    The field name group control value. This acts as an array container for the field.
 *                                       For example if the field has name="foo" and the group value is set to "bar" then the
 *                                       full field name would end up being "bar[foo]".
 * @param   Registry           $input    An optional Registry object with the entire data set to validate against the entire form.
 * @param   Form               $form     The form object for which the field is being tested.
 *
 * @return  boolean  True if the value is valid, false otherwise.
 *
 * @since   1.7.0
 */
public function test(\SimpleXMLElement $element, $value, $group = null, Registry $input = null, Form $form = null)
{
    // Check if the field is required.
    $required = (string) $element['required'] === 'true' || (string) $element['required'] === 'required';
    // Check if the value is empty.
    $blank = empty($value) && $value !== '0' && $value !== 0 && $value !== 0.0;
    if (!$required && $blank) {
        return true;
    }
    // Make an array of all available option values.
    $options = array();
    // Create the field
    $field = null;
    if ($form) {
        $field = $form->getField((string) $element->attributes()->name, $group);
    }
    // When the field exists, the real options are fetched.
    // This is needed for fields which do have dynamic options like from a database.
    if ($field && \is_array($field->options)) {
        foreach ($field->options as $opt) {
            $options[] = $opt->value;
        }
    } else {
        foreach ($element->option as $opt) {
            $options[] = $opt->attributes()->value;
        }
    }
    // There may be multiple values in the form of an array (if the element is checkboxes, for example).
    if (\is_array($value)) {
        // If all values are in the $options array, $diff will be empty and the options valid.
        $diff = array_diff($value, $options);
        return empty($diff);
    } else {
        // In this case value must be a string
        return \in_array((string) $value, $options);
    }
}