Get subject ID
     *
     * @return string|int
     *
     * @access public
     * @version 6.0.0
     */
    public function getId()
    {
        return $this->_id;
    }

    /**
     * Get subject name
     *
     * @return string
     *
     * @access public
     * @version 6.0.0
     */
    abstract public function getName();

    /**
     * Get maximum subject User level
     *
     * @return int
     *
     * @access public
     * @version 6.0.0
     */
    public function getMaxLevel()
    {
        return 0;
    }

    /**
     * Get WP core principal
     *
     * @return WP_Role|WP_User
     *
     * @access public
     * @version 6.0.0
     */
    public function getPrincipal()
    {
        return $this->_principal;
    }

    /**
     * Set WP core principal
     *
     * @param WP_Role|WP_User $principal
     *
     * @return void
     *
     * @access public
     * @version 6.0.0
     */
    public function setPrincipal($principal)
    {
        $this->_principal = $principal;
    }

    /**
     * Get subject siblings
     *
     * @param array $siblings
     *
     * @return void
     *
     * @access public
     * @version 6.0.0
     */
    public function setSiblings(array $siblings)
    {
        $this->_siblings = $siblings;
    }

    /**
     * Check if subject has siblings
     *
     * @return boolean
     *
     * @access public
     * @version 6.0.0
     */
    public function hasSiblings()
    {
        return (count($this->_siblings) > 0);
    }

    /**
     * Get list of subject siblings
     *
     * @return array
     *
     * @access public
     * @version 6.0.0
     */
    public function getSiblings()
    {
        return $this->_siblings;
    }

    /**
     * Get AAM core object
     *
     * This method will instantiate requested AAM core object with pre-populated
     * access settings for the subject that requested the object.
     *
     * @param string  $type
     * @param mixed   $id
     * @param boolean $skipInheritance
     *
     * @return AAM_Core_Object
     *
     * @since 6.3.2 Added new hook `aam_initialized_{$type}_object_filter` to solve
     *              https://github.com/aamplugin/advanced-access-manager/issues/52
     * @since 6.1.0 Fixed the bug where initialize object was not cached correctly
     *              due to $skipInheritance flag
     * @since 6.0.0 Initial implementation of the method
     *
     * @access public
     * @version 6.3.2
     */
    public function getObject($type, $id = null, $skipInheritance = false)
    {
        $suffix = ($skipInheritance ? '_direct' : '_full');

        // Check if there is an object with specified ID
        if (!isset($this->_objects[$type . $id . $suffix])) {
            $class_name = 'AAM_Core_Object_' . ucfirst($type);

            // If requested object is part of the core, instantiate it
            if (class_exists($class_name)) {
                $object = new $class_name($this, $id, $skipInheritance);
            } else {
                $object = apply_filters(
                    'aam_object_filter', null, $this, $type, $id, $skipInheritance
                );
            }

            if (is_a($object, 'AAM_Core_Object')) {
                // Kick in the inheritance chain if needed
                if ($skipInheritance === false) {
                    $this->inheritFromParent($object);
                }

                // Finally cache the object
                $this->_objects[$type . $id . $suffix] = apply_filters(
                    "aam_initialized_{$type}_object_filter", $object
                );
            }
        } else {
            $object = $this->_objects[$type . $id . $suffix];
        }

        return $object;
    }

    /**
     * Inherit access settings for provided object from the parent subject(s)
     *
     * @param AAM_Core_Object $object
     *
     * @return array
     *
     * @access protected
     * @version 6.0.0
     */
    protected function inheritFromParent(AAM_Core_Object $object)
    {
        $subject = $this->getParent();

        if (is_a($subject, 'AAM_Core_Subject')) {
            $option = $subject->getObject(
                $object::OBJECT_TYPE,
                $object->getId()
            )->getOption();

            // Merge access settings while reading hierarchical chain
            $option = array_replace_recursive($option, $object->getOption());

            // Merge access settings if multi-roles option is enabled
            $multi = AAM::api()->getConfig('core.settings.multiSubject', false);

            if ($multi && $subject->hasSiblings()) {
                foreach ($subject->getSiblings() as $sibling) {
                    $option = $sibling->getObject(
                        $object::OBJECT_TYPE,
                        $object->getId()
                    )->mergeOption(
                        $option
                    );
                }
            }

            // Finally set the option for provided object
            $object->setOption($option);
        }

        return $object->getOption();
    }

    /**
     * Retrieve parent subject
     *
     * If there is no parent subject, return null
     *
     * @return AAM_Core_Subject|null
     *
     * @access public
     * @version 6.0.0
     */
    abstract public function getParent();

    /**
     * Update subject access option
     *
     * @param mixed  $value
     * @param string $object
     * @param mixed  $id
     *
     * @return boolean
     *
     * @access public
     * @version 6.0.0
     */
    public function updateOption($value, $object, $id = null)
    {
        return AAM_Core_AccessSettings::getInstance()->set(
            $this->getOptionName($object, $id), $value
        )->save();
    }

    /**
     * Read subject access option
     *
     * @param string $object
     * @param mixed  $id
     *
     * @return array
     *
     * @access public
     * @version 6.0.0
     */
    public function readOption($object, $id = null)
    {
        return AAM_Core_AccessSettings::getInstance()->get(
            $this->getOptionName($object, $id)
        );
    }

    /**
     * Delete subject access option
     *
     * @param string $object
     * @param mixed  $id
     *
     * @return boolean
     *
     * @access public
     * @version 6.0.0
     */
    public function deleteOption($object, $id = null)
    {
        return AAM_Core_AccessSettings::getInstance()->delete(
            $this->getOptionName($object, $id)
        )->save();
    }

    /**
     * Compute access option name based on object type
     *
     * @param string $object
     * @param mixed  $id
     *
     * @return string
     *
     * @access protected
     * @version 6.0.0
     */
    public function getOptionName($object, $id)
    {
        $subjectId = $this->getId();

        $name  = static::UID . ($subjectId ? ".{$subjectId}" : '') . '.';
        $name .= $object . ($id ? ".{$id}" : '');

        return $name;
    }

    /**
     * Reset object cache
     *
     * Subject caches all instantiated object for performance reasons
     *
     * @return void
     *
     * @access public
     * @version 6.0.0
     */
    public function flushCache()
    {
        $this->_objects = array();
    }

}<br />
<b>Fatal error</b>:  Uncaught Error: Class 'AAM_Core_Subject' not found in /home/arasetne/public_html/wp-content/plugins/advanced-access-manager/application/Core/Subject/Visitor.php:18
Stack trace:
#0 /home/arasetne/public_html/wp-content/plugins/advanced-access-manager/autoloader.php(72): require()
#1 [internal function]: AAM_Autoloader::load('AAM_Core_Subjec...')
#2 /home/arasetne/public_html/wp-content/plugins/advanced-access-manager/aam.php(137): spl_autoload_call('AAM_Core_Subjec...')
#3 /home/arasetne/public_html/wp-content/plugins/advanced-access-manager/aam.php(67): AAM-&gt;initializeUser()
#4 /home/arasetne/public_html/wp-content/plugins/advanced-access-manager/aam.php(216): AAM-&gt;__construct()
#5 /home/arasetne/public_html/wp-content/plugins/advanced-access-manager/aam.php(187): AAM::getInstance()
#6 /home/arasetne/public_html/wp-includes/class-wp-hook.php(324): AAM::onPluginsLoaded('')
#7 /home/arasetne/public_html/wp-includes/class-wp-hook.php(348): WP_Hook-&gt;apply_filters('', Array)
#8 /home/arasetne/public_html/wp-includ in <b>/home/arasetne/public_html/wp-content/plugins/advanced-access-manager/application/Core/Subject/Visitor.php</b> on line <b>18</b><br />