Error on Mantis 1.3.0, php7, Ubuntu 16.04

[br8kwall]

Clean installed Ubuntu 16.04 at Digital Ocean with Apache2, MySQL, php7. Updated php.ini to provide mysqli, ran the installer with no issues, and went to login_page.php to login for the first time. However, this page throws a 500 error. I actually got this on earlier installs and so I must be doing something systematically wrong.

Versions:
Apache/2.4.18 (Ubuntu)
PHP 7.0.4-7ubuntu2.1 (cli) ( NTS ) with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2016, by Zend Technologies
mysql -V = mysql Ver 14.14 Distrib 5.7.12, for Linux (x86_64)


Offending line from apache error.log

[Thu Jul 14 23:05:37.570837 2016] [:error] [pid 31942] PHP Fatal error: Uncaught Error: Call to undefined function utf8_decode() in /var/www/html/mantis/library/utf8/native/core.php:34\nStack trace:\n#0 /var/www/html/mantis/core/user_api.php(379): utf8_strlen('')\n#1 /var/www/html/mantis/login_page.php(65): user_is_name_valid('')\n#2 {main}\n thrown in /var/www/html/mantis/library/utf8/native/core.php on line 34

mysqli appears to be loading....

php -r 'phpinfo();' | grep -i mysqli
/etc/php/7.0/cli/conf.d/20-mysqli.ini,
mysqli
MysqlI Support => enabled
mysqli.allow_local_infile => On => On
mysqli.allow_persistent => On => On
mysqli.default_host => no value => no value
mysqli.default_port => 3306 => 3306
mysqli.default_pw => no value => no value
mysqli.default_socket => no value => no value
mysqli.default_user => no value => no value
mysqli.max_links => Unlimited => Unlimited
mysqli.max_persistent => Unlimited => Unlimited
mysqli.reconnect => Off => Off
mysqli.rollback_on_cached_plink => Off => Off
API Extensions => mysqli,pdo_mysql

[br8kwall]

Error is solved by:

sudo apt-get install php7.0-xml

[atrol]

Thanks for telling the solution.
I am quite sure we will more users will see this problem.