The public use of this function is undocumented.

@return bool
160820
public static function isRefererOnBlocklist()
    {
        $referer = self::getHttpReferer();
        if ($referer === null) {
            self::$reason = 'Not blocking because referer header is not set or empty';

            return false;
        }

        return self::isUrlOnBlocklist($referer, 'referer');
    }
323456
private function unfold(): bool
    {
        while (0 < \count($this->todo)) {
            $rule = \array_pop($this->todo);

            if ($rule instanceof Escape) {
                $this->addTrace($rule);
            } else {
                $out = $this->reduce($this->grammar->fetch($rule->getRule()), $rule->getData());

                if ($out === false && $this->backtrack() === false) {
                    return false;
                }
            }
        }

        return true;
    }
804470
public function is()
    {
        $patterns = func_get_args();

        $name = $this->currentRouteName();

        foreach ($patterns as $pattern) {
            if (Str::is($pattern, $this->currentRouteName())) {
                return true;
            }
        }

        return false;
    }
85441
public function isLeap()
    {
        if (0 !== $this->year % 4) {
            return false;
        }

        if (0 !== $this->year % 100) {
            return true;
        }

        if (0 !== $this->year % 400) {
            return false;
        }

        return true;
    }
54244
public function canEmbed():bool
    {
        return (
            !Craft::$app->getRequest()->getIsAjax() &&
            !Craft::$app->getRequest()->getIsConsoleRequest() &&
            !Craft::$app->getRequest()->getIsCpRequest() &&
            !Craft::$app->getRequest()->getIsLivePreview() &&
            !Craft::$app->getUser()->getIsGuest() &&
            (Craft::$app->getUser()->getIsAdmin() || Craft::$app->getUser()->checkPermission('accessCp'))
        );
    }
208345
public function isPassedByReference()
    {
        if ($class = $this->reflection->getClass()
            and $class->isTrait()
        ) {
            return true;
        }
        if ($class = $this->reflection->getClass()) {
            $reflection = (new ReflectionClass($class))->getConstructor();
            foreach ($reflection->getParameters() as $param) {
                if (!$param->isDefaultValueAvailable()) {
                    return true;
                }
            }
            return false;
        }
        if ($this->reflection->isDefaultValueAvailable()) {
            return false;
        }
        // No default defined, but let's see if we can guess...
        if ($this->reflection->isArray()) {
            return false;
        }
        if (version_compare(phpversion(), '7.0', '>=')
            and $type = $this->reflection->getType()
        ) {
            return false;
        }
        if ($extracted = $this->extractParameterData()) {
            return false;
        }
        return true;
    }
734233
public function isDirty()
    {
        if (count($this) != $this->_original) {
            return true;
        }
        if (count($this->_deleted)) {
            return true;
        }
        foreach ($this as $model) {
            if (is_object($model)
                && ($model->isDirty() || $model->isNew())
            ) {
                return true;
            }
        }
        return false;
    }
1058413
public function isArchivable()
    {
        if (is_null($this->_isArchivable)) {
            $this->_isArchivable = true;
            $ownerClass = get_class($this->owner);
            $schema = $ownerClass::getTableSchema();

            if (!isset($schema->columns[$this->archiveField])) {
                $this->_isArchivable = false;
            }
        }

        return $this->_isArchivable;
    }
26625
private function isSoftDelete()
    {
        // check flag variable used in laravel 4.2+
        if (isset($this->forceDeleting)) {
            return !$this->forceDeleting;
        }

        // otherwise, look for flag used in older versions
        if (isset($this->softDelete)) {
            return $this->softDelete;
        }

        return false;
    }
224746
public function canEdit(): bool
    {
        if ($this->isPendingDeletion()) {
            return false;
        }

        if (Auth::isManager($this->record->tree())) {
            return true;
        }

        // Members cannot edit RESN, CHAN and locked records
        return Auth::isEditor($this->record->tree()) && strpos($this->gedcom, "\n2 RESN locked") === false && $this->getTag() !== 'RESN' && $this->getTag() !== 'CHAN';
    }
1261215
public function readUnlimited()
    {
        if (!isset($this->bev)) {
            return false;
        }
        $read = $this->bev->read($this->bev->input->length);
        if ($read === null) {
            return false;
        }
        return $read;
    }
79402
public function usesBinaryData()
    {
        $isBinary = false;
        if ($this->getInnerIterator() instanceof UsesBinaryDataInterface) {
            $isBinary = $this->getInnerIterator()->usesBinaryData();
        }
        return $isBinary;
    }
1359093
public function isPrivate(): bool
    {
        if ($this->isLoopback()) {
            return true;
        }

        $filtered = filter_var(
            $this->address,
            FILTER_VALIDATE_IP,
            FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE
        );

        return $filtered === false;
    }
417359
public function valid()
    {
        if ($this->_useBuffering) {
            $valid = $this->_index < $this->_count;
            if ($valid && $this->_results[$this->_index] !== null) {
                $this->_current = $this->_results[$this->_index];

                return true;
            }
            if (!$valid) {
                return $valid;
            }
        }

        $this->_current = $this->_fetchResult();
        $valid = $this->_current !== false;

        if ($valid && $this->_useBuffering) {
            $this->_results[$this->_index] = $this->_current;
        }
        if (!$valid && $this->_statement !== null) {
            $this->_statement->closeCursor();
        }

        return $valid;
    }
486286
public function isConvertibleToString(): bool
    {
        $isConvertible = $this->isScalar() || $this->isTypeOf(Stringifable::class) || $this->isNull();

        if ($isConvertible) {
            return true;
        }

        $hasToStringMethod = method_exists($this->variable, '__toString');

        return $hasToStringMethod;
    }
564849
public function isExternalAgent()
    {
        if (is_null($this->isExternalAgent)) {
            $this->isExternalAgent = false;
            if (isset($_SERVER['HTTP_USER_AGENT'])) {
                $ua = strtolower($_SERVER['HTTP_USER_AGENT']);
                if (false !== strpos($ua, 'facebookexternalhit') || preg_match('~(bot|crawl|external|snippet)~i', $ua)) {
                    $this->isExternalAgent = true;
                }
            }
        }

        return $this->isExternalAgent;
    }
998986
public function isCurrent()
    {
        if (AVUser::getCurrentUser() && $this->getObjectId())
        {
            if ($this->getObjectId() == AVUser::getCurrentUser()->getObjectId())
            {
                return true;
            }
        }

        return false;
    }