Even better debugging; Equipped yourself with powerful tools.

Even Better DebuggingEquipped yourself with powerful debug tools

Murshed Ahmmad Khan

Sunday, November 7, 2010

presented at phpxperts seminar 2010

6th November, 2010


http://livepage.apple.com/

http://livepage.apple.com/

“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 = OnThis 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 = OnWrite/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 oncephp.ini directive default value Purpose Example recommendations

display_errors OnPrint out errors as part of the

outputdisplay_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


http://xdebug.org/

http://xdebug.org/

Xdebug featuresstack 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)


http://code.activestate.com/komodo/remotedebugging/


Download Xdebug binaries (cont...)



http://code.activestate.com/komodo/




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 VariablesXdebug.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)


Referenceshttp://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


http://www.xdebug.org




http://derickrethans.nl/talks.php

http://derickrethans.nl/talks.php





who am imurshed ahmmad Khansoftware engineer, somewhere in... also a bug hunter, code ninja

stay tuned for the updated slides at: http://www.usamurai.comtwitter: @usamurai. email: [email protected]


http://www.somewherein.net

http://www.somewherein.net

http://www.usamurai.com

http://www.usamurai.com

Thanks!

No Questions?! :)


Even better debugging; Equipped yourself with powerful tools.

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