PHP Startup: Unable to load dynamic library for PHP folder

your php .ini configuration file(s) makes references to several files that does not exist, for instance /usr/lib/php/20131226/php_pdo_mysql.dll, your php installation has been corrupted. it's probably easier to just re-install PHP, but if you want to repair it manually, make a page called phpinfo.php and have it contain

<?php phpinfo(~0);

and open it in a browser, you will get the location of php.ini and a list of additional ini configuration files parsed, and once you have that, scan the php.ini file, and all additional configuration files, and remove all references to the files that does not exist. for example in this screenshot:

here you'd have to scan the files /etc/php/7.0/fpm/php.ini and /etc/php/7.0/fpm/conf.d/10-mysqlnd.ini and /etc/php/7.0/fpm/conf.d/10-opcache.ini and /etc/php/7.0/fpm/conf.d/10-pdo.ini and /etc/php/7.0/fpm/conf.d/15-xml.ini and /etc/php/7.0/fpm/conf.d/20-calendar.ini and /etc/php/7.0/fpm/conf.d/20-ctype.ini and /etc/php/7.0/fpm/conf.d/20-curl.ini and /etc/php/7.0/fpm/conf.d/20-dom.ini and /etc/php/7.0/fpm/conf.d/20-exif.ini and /etc/php/7.0/fpm/conf.d/20-fileinfo.ini and /etc/php/7.0/fpm/conf.d/20-ftp.ini and /etc/php/7.0/fpm/conf.d/20-gd.ini and /etc/php/7.0/fpm/conf.d/20-gettext.ini and /etc/php/7.0/fpm/conf.d/20-iconv.ini and /etc/php/7.0/fpm/conf.d/20-json.ini and /etc/php/7.0/fpm/conf.d/20-mbstring.ini and /etc/php/7.0/fpm/conf.d/20-mysqli.ini and /etc/php/7.0/fpm/conf.d/20-pdo_mysql.ini and /etc/php/7.0/fpm/conf.d/20-pdo_sqlite.ini and /etc/php/7.0/fpm/conf.d/20-phar.ini and /etc/php/7.0/fpm/conf.d/20-posix.ini and /etc/php/7.0/fpm/conf.d/20-readline.ini and /etc/php/7.0/fpm/conf.d/20-shmop.ini and /etc/php/7.0/fpm/conf.d/20-simplexml.ini and /etc/php/7.0/fpm/conf.d/20-sockets.ini and /etc/php/7.0/fpm/conf.d/20-sqlite3.ini and /etc/php/7.0/fpm/conf.d/20-ssh2.ini and /etc/php/7.0/fpm/conf.d/20-sysvmsg.ini and /etc/php/7.0/fpm/conf.d/20-sysvsem.ini and /etc/php/7.0/fpm/conf.d/20-sysvshm.ini and /etc/php/7.0/fpm/conf.d/20-tokenizer.ini and /etc/php/7.0/fpm/conf.d/20-wddx.ini and /etc/php/7.0/fpm/conf.d/20-xdebug.ini and /etc/php/7.0/fpm/conf.d/20-xmlreader.ini and /etc/php/7.0/fpm/conf.d/20-xmlwriter.ini and /etc/php/7.0/fpm/conf.d/20-xsl.ini for references to the files that does not exist, and remove those references... have fun

(but seriously, you'd probably be better off just re-installing the requred version of PHP. by your comments, i see you already have multiple versions of PHP installed.)