Even better debugging; Equipped yourself with powerful tools.

Even Better Debugging
Equipped yourself with powerful debug tools
Murshed Ahmmad Khan
Sunday, November 7, 2010

presented at phpxperts
seminar 2010
6th November, 2010

“The defect is the crime; debugging is
the punishment”
Cause nobody’s perfect; study says we use 80% of
our time to maintain the old codes.

Frustrating!! blank pages?
Think!! what does a blank page mean? What happened?

Let’s have a quick recap of the
available error settings in PHP

display_errors = On
This determines whether errors should be
printed to the screen as part of the script
output; depending on the error_reporting value.
It is strongly recommended to turn
it “Off” in the production server.
Default value is “On”.

log_errors = On
Write/log errors into a server side
log ﬁle; deﬁned by “error_log”
It is strongly recommended to turn
log_errors “On” in place of display_errors
in the production web sites.
Default value is “Off”.

error_reporting = E_ALL
What type of errors, notices, warnings need
to be notiﬁed/write by the php interpreter.
Default value is E_ALL & ~ E_NOTICE
When developing best practice is to use
E_ALL. Or even better E_ALL | E_STRICT.

Error directives... All at once
php.ini directive default value Purpose Example recommendations
display_errors On
Print out errors
as part of the
output
display_errors = On
strongly
recommended to
turn it off in
production
log_errors Off
log errors into a
log ﬁle
log_errors = On
strongly recommended
to turn it on in
production
error_reporting
E_ALL &
~E_NOTICE
what type of
errors need to be
notiﬁed and/or
logged
error_reporting =
E_ALL
show all errors except
notices:
E_ALL & ~ E_NOTICE
for development in php5,
show all type of errors:
E_ALL | E_STRICT
*from php6 E_STRICT will
also be included in E_ALL

Revisiting the blank page...
TextText
browser o/p

Revisiting the blank page...
erroneous
script
server error log

Controlling php error reporting
from apache httpd.conf
Sometimes turning error reporting on in
php.ini may not work.
It’s good to know how to set these
conﬁguration variables from server side.
Setting these in httpd.conf ﬁle overrides all
php.ini & guarantee to set the error levels.

Controlling php error reporting
from apache(cont...)
[+] Add the below lines in httpd.conf ﬁle:
the integer value 2039 stands for E_ALL &
~E_NOTICE
There are different integer values for each error
types
[+] php_ﬂag display_errors on
[+] php_value error_reporting 2039

Setting the error directives at
runtime from the php scripts
It won’t affect if script has fatal errors cause
it might not get executed.
ini_set(‘display_errors’, 1);
ini_set(‘error_reporting’, E_ALL);
// error_reporting(E_ALL);

For variable debugging, use reusable method
var_debug($dataNodes,true);
function var_debug( $item, $exit=false )
{
$op = '<pre>DEBUG INFO</pre>';
$op .= '<pre>' . print_r( $item, true ) . '</pre>';
if( is_production() ){
$op = ‘’;
//return false;
}
echo $op;
if( $exit ){ exit(); }
}

Don’t code all of the time! Rather
equipped yourself with powerful tools!!

Xdebug

What is Xdebug?
Xdebug is one of the most popular
debugging engines in PHP
A PHP extension about 8 years old
Uses DBGp debugging protocol

Xdebug features
stack traces
inﬁnite recursion protection
colored var_dump()
function traces

Xdebug features(Cont...)
code coverage reports
proﬁling / performance
analysis
remote debugging
a whole lot other features

Installing Xdebug [by PEAR/
PECL]
# pecl install xdebug
As easy as one command!

Installing Xdebug[PEAR/
PECL cont...]
Ignore any prompt: you should add
“extension=xdebug.so” in php.ini
[+] Add the correct line in your php.ini ﬁle:
[+] zend_extension = “/usr/local/
php/modules/xdebug.so”

Installing Xdebug(By
Downloading)
Activestate site has binary packages
available for all versions of php in all
platforms(Windows/MacOSX/Linux)

Download Xdebug binaries
(cont...)
http://code.activestate.com/komodo/
remotedebugging/

Download xDebug...(Grab the
extension as per your PHP version

Xdebug Installation(contd...)
paste the xdebug.so/xdebug.dll file into the
extension directory
[+]Add the extension path in the php.ini
[xdebug]
zend_extension = “/Applications/MAMP/bin/php5/
lib/php/extensions/no-debug-non-zts-20060613/
xdebug.so”
xdebug.file_link_format = “txmt://open?url=file://
%f&line=%1”

Xdebug in action!
restart apache and you’re done!!
xdebug now replaces traditional error messages
with more helpful debug information.

Xdebug: Stack Traces

Debug Request Variables
Xdebug.dump.GET = *

Debug Request Variables
Xdebug.dump.GET = *
Xdebug.dump.POST = *
Also for: COOKIE, ENV, FILES, REQUEST,
SERVER and SESSION

xdebug: Code Coverage
xdebug_start_code_coverage();
var_dump( xdebug_get_code_coverage);
xdebug_stop_code_coverage();
Tells you which lines of script have been
executed during the request.

Code Coverage(Contd...)

Remote Debugging(step by step
debugging with IDE or any DbGp
interface)
[+] php.ini settings:
xdebug.remote_enable=1
xdebug.remote_handler=dbgp
xdebug.remote_host=localhost
xdebug.remote_port=9000
xdebug.extended_info=1

Powerful code proﬁling with Xdebug

Powerful code proﬁling with Xdebug
(Contd...)
WinCacheGrind: for windows
kCacheGrind: for linux
Webgrind: for all platforms
Easy Xdebug: browser extensions
(ﬁrefox addon)

References
http://www.xdebug.org
http://www.xdebug.org/docs.php
xdebug slides: http://derickrethans.nl/talks.php
http://www.devshed.com/c/a/PHP/Error-and-
Exception-Handling-in-PHP/
http://www.php.net/manual/en/debugger-
about.php

who am i
murshed ahmmad Khan
software engineer, somewhere in...
also a bug hunter, code ninja
stay tuned for the updated slides at:
http://www.usamurai.com
twitter: @usamurai. email: usamurai@gmail.com

Thanks!
No Questions?! :)

Even better debugging; Equipped yourself with powerful tools.

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