Local variables not shown when OPcache is enabled while debugging with Xdebug - php

Question

I have Xdebug enabled and working together with OPcache. OPcache module is loaded first by phpfpm (important). If you try to debug the code below (from the browser) and put a breakpoing in the local variables you will see that they are not displayed. If I deactivate OPCache everything works as expected. I'm using PhpStorm 2018.2.5 to debug.
class Foo {
public $member = 'Some value';
public function methodFoo() {
$localFoo = "local2";
}
}
class Bar {
public $firstMember = "foo";
public $secondMember = "bar";
public function create() {
$localBar = 10;
$newFoo = new Foo();
$newFoo->methodFoo();
$localBar += 1;
$this->firstMember = "Other value";
}
}
$foo = "testing";
$bar = "testing2";
$obj = new Bar();
$obj->create();
I do not know if I miss something or it's a bug. Years ago there was a similar bug in xdebug but it was not related to OPcache:
bug
I leave the information related to my system and the log of Xdebug
phpinfo()
PHP Version => 7.2.10-0ubuntu0.18.04.1
System => Linux pablo-dv6 4.15.0-36-generic #39-Ubuntu SMP Mon Sep 24 16:19:09 UTC 2018 x86_64
Build Date => Sep 13 2018 13:45:02
Server API => Command Line Interface
Virtual Directory Support => disabled
Configuration File (php.ini) Path => /etc/php/7.2/cli
Loaded Configuration File => /etc/php/7.2/cli/php.ini
Scan this dir for additional .ini files => /etc/php/7.2/cli/conf.d
Additional .ini files parsed => /etc/php/7.2/cli/conf.d/10-opcache.ini,
/etc/php/7.2/cli/conf.d/10-pdo.ini,
/etc/php/7.2/cli/conf.d/15-xml.ini,
/etc/php/7.2/cli/conf.d/20-calendar.ini,
/etc/php/7.2/cli/conf.d/20-ctype.ini,
/etc/php/7.2/cli/conf.d/20-curl.ini,
/etc/php/7.2/cli/conf.d/20-dom.ini,
/etc/php/7.2/cli/conf.d/20-exif.ini,
/etc/php/7.2/cli/conf.d/20-fileinfo.ini,
/etc/php/7.2/cli/conf.d/20-ftp.ini,
/etc/php/7.2/cli/conf.d/20-gettext.ini,
/etc/php/7.2/cli/conf.d/20-iconv.ini,
/etc/php/7.2/cli/conf.d/20-intl.ini,
/etc/php/7.2/cli/conf.d/20-json.ini,
/etc/php/7.2/cli/conf.d/20-mbstring.ini,
/etc/php/7.2/cli/conf.d/20-pdo_sqlite.ini,
/etc/php/7.2/cli/conf.d/20-phar.ini,
/etc/php/7.2/cli/conf.d/20-posix.ini,
/etc/php/7.2/cli/conf.d/20-readline.ini,
/etc/php/7.2/cli/conf.d/20-shmop.ini,
/etc/php/7.2/cli/conf.d/20-simplexml.ini,
/etc/php/7.2/cli/conf.d/20-sockets.ini,
/etc/php/7.2/cli/conf.d/20-sqlite3.ini,
/etc/php/7.2/cli/conf.d/20-sysvmsg.ini,
/etc/php/7.2/cli/conf.d/20-sysvsem.ini,
/etc/php/7.2/cli/conf.d/20-sysvshm.ini,
/etc/php/7.2/cli/conf.d/20-tokenizer.ini,
/etc/php/7.2/cli/conf.d/20-wddx.ini,
/etc/php/7.2/cli/conf.d/20-xmlreader.ini,
/etc/php/7.2/cli/conf.d/20-xmlwriter.ini,
/etc/php/7.2/cli/conf.d/20-xsl.ini,
/etc/php/7.2/cli/conf.d/20-zip.ini,
/etc/php/7.2/cli/conf.d/30-xdebug.ini
PHP API => 20170718
PHP Extension => 20170718
Zend Extension => 320170718
Zend Extension Build => API320170718,NTS
PHP Extension Build => API20170718,NTS
Debug Build => no
Thread Safety => disabled
Zend Signal Handling => enabled
Zend Memory Manager => enabled
Zend Multibyte Support => provided by mbstring
IPv6 Support => enabled
DTrace Support => available, disabled
Registered PHP Streams => https, ftps, compress.zlib, php, file, glob, data, http, ftp, phar, zip
Registered Stream Socket Transports => tcp, udp, unix, udg, ssl, tls, tlsv1.0, tlsv1.1, tlsv1.2
Registered Stream Filters => zlib.*, string.rot13, string.toupper, string.tolower, string.strip_tags, convert.*, consumed, dechunk, convert.iconv.*
This program makes use of the Zend Scripting Language Engine:
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
with Zend OPcache v7.2.10-0ubuntu0.18.04.1, Copyright (c) 1999-2018, by Zend Technologies
with Xdebug v2.6.1, Copyright (c) 2002-2018, by Derick Rethans
Zend OPcache
Opcode Caching => Disabled
Optimization => Disabled
SHM Cache => Enabled
File Cache => Disabled
Startup Failed => Opcode Caching is disabled for CLI
Directive => Local Value => Master Value
opcache.blacklist_filename => no value => no value
opcache.consistency_checks => 0 => 0
opcache.dups_fix => Off => Off
opcache.enable => On => On
opcache.enable_cli => Off => Off
opcache.enable_file_override => Off => Off
opcache.error_log => no value => no value
opcache.file_cache => no value => no value
opcache.file_cache_consistency_checks => 1 => 1
opcache.file_cache_only => 0 => 0
opcache.file_update_protection => 2 => 2
opcache.force_restart_timeout => 180 => 180
opcache.huge_code_pages => Off => Off
opcache.inherited_hack => On => On
opcache.interned_strings_buffer => 8 => 8
opcache.lockfile_path => /tmp => /tmp
opcache.log_verbosity_level => 1 => 1
opcache.max_accelerated_files => 10000 => 10000
opcache.max_file_size => 0 => 0
opcache.max_wasted_percentage => 5 => 5
opcache.memory_consumption => 128 => 128
opcache.opt_debug_level => 0 => 0
opcache.optimization_level => 0x7FFFBFFF => 0x7FFFBFFF
opcache.preferred_memory_model => no value => no value
opcache.protect_memory => 0 => 0
opcache.restrict_api => no value => no value
opcache.revalidate_freq => 2 => 2
opcache.revalidate_path => Off => Off
opcache.save_comments => 1 => 1
opcache.use_cwd => On => On
opcache.validate_permission => Off => Off
opcache.validate_root => Off => Off
opcache.validate_timestamps => On => On
Xdebug log related to this part (you can see that $localBar doesn't appear):
<- context_get -i 46 -d 0 -c 0
-> <response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="http://xdebug.org/dbgp/xdebug" command="context_get" transaction_id="46" context="0"><property name="$newFoo" fullname="$newFoo" type="uninitialized"></property><property name="$this" fullname="$this" type="object" classname="Bar" children="1" numchildren="2" page="0" pagesize="100"><property name="firstMember" fullname="$this->firstMember" facet="public" type="string" size="3" encoding="base64"><![CDATA[Zm9v]]></property><property name="secondMember" fullname="$this->secondMember" facet="public" type="string" size="3" encoding="base64"><![CDATA[YmFy]]></property></property></response>
Any help is welcome, thanks :)

Answer 1

I answer myself, in case it serves to someone.
This is a feature of OPCache. It optimizes PHP code by sometimes removing variables if they are not needed.
Solution: disable OPCache when debugging.
sudo phpdismod opcache
And restart phpfpm or apache according to your environment
sudo service php7.2-fpm restart
or
sudo service apache2 restart
More info here.

Answer 2

It's a late answer, but the accepted one is not entirely correct. The problem is not that you cannot use OPCache with xdebug. You can, but you have to load the OPCache extension BEFORE xdebug. To quote the documentation:
If you want to use Xdebug and OPCache together, you must have the
zend_extension line for Xdebug below the line for OPCache, or in a
file starting with a higher number (ie. 99-xdebug.ini vs
20-opcache.ini), otherwise they won't work properly together.