I had php5-fpm, nginx, mysql, phpmyadmin that installed on my ubuntu 14.04. every thing was good. When I updated php to php7.0 phpmyadmin required to install mbstring. I installed it and works well. But Export page of phpmyadmin show blank page.
This error is logged in nginx error log file.
2016/08/09 16:20:31 [error] 1494#0: *35 FastCGI sent in stderr: "PHP message: PHP Fatal error: Cannot 'break' 2 levels in /usr/share/phpmyadmin/export.php on line 864" while reading response header from upstream, client: 127.0.0.1, server: localhost, request: "POST /phpmyadmin/export.php HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.0-fpm.sock:", host: "localhost", referrer: "http://localhost/phpmyadmin/index.php?token=584932884866cc16a2444d67eb7927d0&phpMyAdmin=4aro5gojhjuli0svkuctbrlot0450dar"