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

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="$this-&gt;firstMember" facet="public" type="string" size="3" encoding="base64"><![CDATA[Zm9v]]></property><property name="secondMember" fullname="$this-&gt;secondMember" facet="public" type="string" size="3" encoding="base64"><![CDATA[YmFy]]></property></property></response>

Any help is welcome, thanks :)

Why do you think it's a bug? It's just a plain optimisation.. as your variable is not used anywhere (same as if it would not exist). — LazyOne
– LazyOne, Commented Oct 16, 2018 at 18:51
It's not true. You can use the variable and the behavior is the same. That is not the problem at all. Check it out for yourself if you want. @LazyOne — Pablo Soria
– Pablo Soria, Commented Oct 16, 2018 at 19:06
How do you debug from the browser? As far as I know debugging flag is passed to PHPStorm to initiate debugging session and all debugging is done in it. — Daniel Protopopov
– Daniel Protopopov, Commented Oct 16, 2018 at 19:32
OK -- where (at what stage) it does not work? Screenshots please. I've tested your code in PhpStorm 2018.2.5 with PHP 7.2.9 x32, Xdebug 2.6.0, OPCache 7.2.9 (Windows 10) and it seemed to work fine (in a CLI thought). But yes, I've seen other people stating similar issues... — LazyOne
– LazyOne, Commented Oct 16, 2018 at 21:24
Checked via browser .... and I do see missing of some variables. I've added few echo statements... and do not see any output. But after modifying things a bit here and there (added more code etc) -- it worked for me. It also work sin real code when debugging ... so don't know what to think about this. — LazyOne
– LazyOne, Commented Oct 16, 2018 at 21:31

Pablo Soria · Accepted Answer · 2018-12-18 17:11:32Z

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.

answered Dec 18, 2018 at 17:11

Pablo Soria

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Comments

Aleksander Wons · Accepted Answer · 2022-07-03 13:01:04Z

1

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.

answered Jul 3, 2022 at 13:01

Aleksander Wons

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2 Comments

Faran Cheema Over a year ago

But how to load the OPCache before x-debug?

Aleksander Wons Over a year ago

@FaranCheema Please have a look again at my answer. PHP loads the ini files in alphabetical order.

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