phpmyadmin getCookie() on null

PHP Fatal error:  Uncaught Error: Call to a member function getCookie() on null in /usr/share/phpmyadmin/libraries/classes/Url.php:219
Stack trace:
#0 /usr/share/phpmyadmin/libraries/classes/Url.php(171): PhpMyAdmin\Url::getCommonRaw(Array, '?')
#1 /usr/share/phpmyadmin/libraries/classes/Core.php(762): PhpMyAdmin\Url::getCommon(Array)
#2 /usr/share/phpmyadmin/libraries/classes/Core.php(338): PhpMyAdmin\Core::linkURL('https://secure....')
#3 /usr/share/phpmyadmin/libraries/classes/Core.php(364): PhpMyAdmin\Core::getPHPDocLink('book.json.php')
#4 /usr/share/phpmyadmin/libraries/classes/Core.php(1006): PhpMyAdmin\Core::warnMissingExtension('json', true)//这里提示缺少json扩展
#5 /usr/share/phpmyadmin/libraries/common.inc.php(110): PhpMyAdmin\Core::checkExtensions()
#6 /usr/share/phpmyadmin/index.php(23): require_once('/usr/share/phpm...')
#7 {main}
  thrown in /usr/share/phpmyadmin/libraries/classes/Url.php on line 219

缺少json扩展
安装json扩展解决问题