This is just another interesting problem to solve. I have encountered this subtle difference in PHP packages when I moved personal Dokuwiki instance from Debian Jessie to Debian Stretch.
Operating system version.
$ lsb_release -a
No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 9.3 (stretch) Release: 9.3 Codename: stretch
HTTP error code 500 logged by nginx.
$ tail /var/log/nginx/access.log
[...] 10.250.3.36 - - [11/Jan/2018:14:52:46 +0100] "GET /doku.php?id=start&do=edit HTTP/1.1" 500 5 "http://10.250.4.250/doku.php?id=start" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:57.0) Gecko/20100101 Firefox/57.0" 10.250.3.36 - - [11/Jan/2018:14:52:49 +0100] "GET /doku.php?id=start&do=edit HTTP/1.1" 500 5 "http://10.250.4.250/doku.php?id=start" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:57.0) Gecko/20100101 Firefox/57.0" 10.250.3.36 - - [11/Jan/2018:14:53:50 +0100] "GET /doku.php?id=start&do=edit HTTP/1.1" 500 5 "http://10.250.4.250/doku.php?id=start" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:57.0) Gecko/20100101 Firefox/57.0"
Detailed stack trace by uwsgi pointing to the undefined function utf8_decode().
$ tail /var/log/uwsgi/app/php.log
[pid: 18443|app: -1|req: -1/1] 10.250.3.36 () {44 vars in 977 bytes} [Thu Jan 11 14:52:46 2018] GET /doku.php?id=start&do=edit => generated 0 bytes in 91 msecs (HTTP/1.1 500) 4 headers in 188 bytes (0 switches on core 0)
Thu Jan 11 14:52:49 2018 - PHP Fatal error: Uncaught Error: Call to undefined function utf8_decode() in /srv/dokuwiki/inc/utf8.php:152
Stack trace:
#0 /srv/dokuwiki/inc/utf8.php(402): utf8_strlen('start')
#1 /srv/dokuwiki/inc/common.php(1128): utf8_ucfirst('start')
#2 /srv/dokuwiki/inc/common.php(1073): parsePageTemplate(Array)
#3 /srv/dokuwiki/inc/actions.php(574): pageTemplate('start')
#4 /srv/dokuwiki/inc/actions.php(156): act_edit('edit')
#5 /srv/dokuwiki/doku.php(124): act_dispatch()
#6 {main}
thrown in /srv/dokuwiki/inc/utf8.php on line 152
Install php7.0-xml package to solve this issue.
$ sudo apt-get install php-xml
Reading package lists... Done Building dependency tree Reading state information... Done The following additional packages will be installed: php7.0-xml The following NEW packages will be installed: php-xml php7.0-xml 0 upgraded, 2 newly installed, 0 to remove and 1 not upgraded. Need to get 117 kB of archives. After this operation, 496 kB of additional disk space will be used. Do you want to continue? [Y/n] Get:1 http://ftp.task.gda.pl/debian stretch/main amd64 php7.0-xml amd64 7.0.19-1 [112 kB] Get:2 http://ftp.task.gda.pl/debian stretch/main amd64 php-xml all 1:7.0+49 [5,068 B] Fetched 117 kB in 0s (417 kB/s) Selecting previously unselected package php7.0-xml. (Reading database ... 29079 files and directories currently installed.) Preparing to unpack .../php7.0-xml_7.0.19-1_amd64.deb ... Unpacking php7.0-xml (7.0.19-1) ... Selecting previously unselected package php-xml. Preparing to unpack .../php-xml_1%3a7.0+49_all.deb ... Unpacking php-xml (1:7.0+49) ... Setting up php7.0-xml (7.0.19-1) ... Creating config file /etc/php/7.0/mods-available/dom.ini with new version Creating config file /etc/php/7.0/mods-available/simplexml.ini with new version Creating config file /etc/php/7.0/mods-available/wddx.ini with new version Creating config file /etc/php/7.0/mods-available/xml.ini with new version Creating config file /etc/php/7.0/mods-available/xmlreader.ini with new version Creating config file /etc/php/7.0/mods-available/xmlwriter.ini with new version Creating config file /etc/php/7.0/mods-available/xsl.ini with new version Setting up php-xml (1:7.0+49) ...
Restart uwsgi service.
$ sudo /etc/init.d/uwsgi restart [ ok ] Restarting uwsgi (via systemctl): uwsgi.service.
This happens because utf8_decode() function is now provided by php7.0-xml package in Debian Stretch, but it was provided by libphp5-embed package in Debian Jessie.
Debian Stretch library that contains above-mentioned function:
stretch$ readelf -s /usr/lib/php/20151012/xml.so | grep utf8_decode
75: 0000000000006e20 142 FUNC GLOBAL DEFAULT 11 zif_utf8_decode
98: 0000000000006150 482 FUNC GLOBAL DEFAULT 11 xml_utf8_decode
Debian Jessie library that contains above-mentioned function:
jessie$ readelf -s /usr/lib/libphp5.so | grep utf8_decode
1348: 0000000000351a30 343 FUNC GLOBAL DEFAULT 11 xml_utf8_decode 1598: 0000000000352630 146 FUNC GLOBAL DEFAULT 11 zif_utf8_decode