In depth presentation on setting up, configuring, and trigger PHP Xdebug for step through debugging and code profiling. This presentation will not tell you how to configure your Xdebug client. It will help you understand how to configure and tune Xdebug for web and CLI based debugging and profiling in PHP.

1. Build better code

2. Who Am I?
• Selling Source Direct Lead
Developer
• Coupla CTO
• Founder/Organizer of Las
Vegas PHP Users Group
• Co-Organizer of Las Vegas
Developers Users Group
• PHP Machinist Maintainer
• #VegasTech Enthusiast
Adam Englander
adamenglander@yahoo.com
@adam_englander
http://adamknowsstuff.com
https://github.com/derptest

3. What is Xdebug?
Xdebug is a PHP extension providing:
 Enhanced variable display
 Enhanced stack traces
 Function traces
 Code coverage analysis
 Code profiling
 Remote debugging

4. Who made Xdebug
Xdebug is written by
Derick Rethans.
Derick is also the author
of the PHP MongoDB
extension. If you’d like
to thank Derick, and you
probably should, you
can use his wish list.

5. What we’re not talking about
Enhanced variable display
 Enhanced stack traces
 Function traces
 Code coverage analysis

All of these are nice and all but they aren’t
what were talking about.

6. What we are talking about
Remote debugging:
Step through debugging with a remote
client via the DBGP protocol
Code profiling:
Finding bottlenecks in your code and
visualize those with an external tool such
as KCacheGrind or WinCacheGrind.

7. Xdebug Remote Debugging
Line by line stepping through code.
 Break points to stop at particular areas of
code.
 Variable inspection to be able to see
variable values at a line of code. Death to
var_dump.
 Variable setting to allow replacement of
variable values at runtime.
 The single best way to troubleshoot bugs.


8. Xdebug Profiling
Find bottlenecks
 Timings for optimization
 Similar to Cachegrind but no memory
data
 Output format is standard so it can be
read by standard Cachegrind tools:
Kcachegrind, QCacheGrind,
WinCacheGrind, IDE plugins, etc.


9. Xdebug Requirements

Installing the Xdebug extension
 PEAR/PECL install available
 Available via most Linux package managers
DBGP client for remote debugging –
Debugclient comes with Xdebug source and
a slew of IDEs have built in support.
 Cachegrind analyzer for profiling –
KCachegrind, QCachegrind,
WinCacheGrind, or IDE support.


10. Remote Debug Configuration
extended_info – Enabled by default.
Allows breakpoints.
 idekey – Identifier for the debug session.
Most clients will restrict to requests from
a single idekey value.
 remote_autostart – Disabled by default.
Will start remote debugging with every
request.


11. Remote Debug Configuration
remote_connect_back – Disabled by
default. Helpful for debugging on
shared hosts and virtual machines.
Xdebug session will connect to host
making the request.
 remote_cookie_expire_time – Defaults
to 3600 seconds (60 minutes). The time
the debug session cookie will live.


12. Remote Debug Configuration
remote_enable – Defaults to 0 (off).
Enable remote debugging
 remote_handler – Defaults to DBGP.
You should never have to use anything
else so just leave it.
 remote_host – Remote host with which
Xdebug will connect at the start of an
Xdebug session.


13. Remote Debug Configuration
remote_log – Default value “”. Log all
remote debugger communication. You
will probably never need this unless you
are writing a client or have connectivity
issues.
 remote_mode – Default value is “req”.
Determines how the session is initiated.
“req” will start the session with every
request. “jit” will start the session when
an error condition occurs.


14. Remote Debug Configuration

remote_port – Defaults to 9000. TCP/IP
port of the remote client which which
Xdebug will connect. Most clients
default to 9000 so unless you are forced
to debug multiple remote machines, just
leave it.

15. Profiling Configuration
profiler_append – Default value 0 (off).
Append the profiler output to the same file if
the profile_output_name will allow.
 profiler_enable – Default value 0 (off).
Enable profiling for all requests and script
executions. If you are doing web request
profiling, use profiler_enable_trigger
instead. This should normally be used only
for CLI profiling and configuring via
environment variable.


16. Profiling Configuration
profiler_enable_trigger – Default value 0
(off). Allow triggering of profiling via
request query parameter or cookie with
the name XDEBUG_PROFILE. The
value is optional and ignored.
 profiler_output_dir – Defaults to “/tmp”.
The directory in which the profiler output
file will be written.


17. Profiling Configuration

profiler_output_name – Default value is
“cachegrind.out.%p” where %p is the
process ID of the process running the
profile. There are many variable options
like %s for the file name. See the
Xdebug documentation for details:
http://xdebug.org/docs/all_settings#trace
_output_name

18. Configuring via php.ini
Always prepend option with “xdebug.”
Example:
zend_extension=/usr/local/php/modules/xd
ebug.so
xdebug.remote_enable=1
xdebug.remote_connect_back=1
xdebug.profiler_enable_trigger=1

19. Configuring via .htaccess
If you have no other options, you can use a
.htaccess file if allowed.
Example:
php_flag xdebug.remote_enable true
php_value xdebug.remote_host “10.0.0.2”
php_flag xdebug.profiler_enable_trigger true

20. Configuring via environment

When running CLI scripts, you can configure
Xdebug via the XDEBUG_CONFIG variable
Profiling Example:
export XDEBUG_CONFIG=“profiler_enable=1”
Remote Debugging Example:
export XDEBUG_CONFIG=“idekey=key”

21. Start/Stop Xdebug Sessions
You can start and stop Xdebug remote
debugging and profiling sessions in many
ways:
 IDE integration
 Browser Plugin (Chrome/Firefox/Safari)
 URL parameter
 Cookie
 CLI environment variable
 Xdebug config

22. Start/Stop via IDE
Most IDEs will have a way to start a
remote debug or profiling session from
the command line or web page.
 See the documentation for your IDE to
learn how to use that.


23. Start/Stop via Browser Plugin
Browser plugins are a nice simple way
to start and stop an Xebug session
 Available for most browsers.
 Will automatically (un)set the
XDEBUG_SESSION or
XDEBUG_PROFILE cookie.


24. Start/Stop via URL Parameter
XDEBUG_SESSION_START=idekey
 XDEBUG_SESSION_STOP
 XDEBUG_PROFILE

Example:
http://site.com?XDEBUG_SESSION_START=go
http://site.com?XDEBUG_SESSION_STOP
http://site.com?XDEBUG_PROFILE

25. Start/Stop via Cookie
Use a cookie named XDEBUG_SESSION with
the value being the idekey value.
Remote Debug Example:
curl --cookie=“XDEBUG_SESSION=eclipse” http://host.com
Profiling Example:
curl --cookie=“XDEBUG_PROFILE=1” http://host.com

26. Start/Stop via CLI Environment


XDEBUG_CONFIG environment variable will start
stop CLI Xdebug for profiling and debugging
Can be executed for a single script or multiple scripts
Multi-Command Example:
export XDEBUG_CONFIG=“remote_host=localhost”
php script.php
export XDEBUG_CONFIG=
Single Command Example:
XDEBUG_CONFIG=“profiler_enable=1” php script.php

27. Start/Stop via Xdebug Config
Setting xebug.remote_autostart will start
remote debugging with every execution.
 Setting xdebug.profiler_enable will start
profiling with every execution.
 Requires config change to turn off.
 Try and avoid this. There are so many
better ways.


28. Demo
Here we go with some code and
examples.