Debugging PHP Applications with Xdebug and Eclipse PDT

Posted by on Apr 13, 2008 in Eclipse, Programming, Technology, Web Development66 comments

Xdebug LogoOK, so I have x64 Eclipse successfully installed and running with all the plugins I use for Web Application Development. But what about debugging? Sure, var_dump(), echo, print and so on are all valuable to me when debugging a script, but it’s always good to have more information.

Xdebug is a fantastic PHP extension, which is written by one of the PHP Core Developers, Derick Rethans. The current version is 2.0.3, and I set about installing it on my system, and integrating it into Eclipse PDT today.

Xdebug can be installed in a few different ways – by downloading the binaries from the site, compiling the source, or via PECL:

sudo pecl install xdebug

Some days, I just prefer to download compile the source, as it gives me more of an understanding of what is being installed and where, and this is one of those days:

cd ~/
mkdir xdebug
cd xdebug
tar -zxvf xdebug-2.0.3.tgz
cd xdebug-2.0.3

The packages phpize and php-config are required to install Xdebug, and can be obtained by installing the relevant PHP development packages:

sudo apt-get install php4-dev


sudo apt-get install php5-dev

depending on the PHP version installed. After unzipping the Xdebug source, I ran


which output:

PHP Api Version: 20041225
Zend Module Api No: 20060613
Zend Extension Api No: 220060519

I then checked this against the table at to see if my PHP version (5.2.3) was compatible with Xdebug – it matched up to the table’s 5.2.x PHP version row, so I went ahead and installed:

./configure --enable-xdebug --with-php-config=/usr/bin/php-config

which created a file in the modules subdirectory. This file needs to be copied (or moved) to the PHP Extension directory, which on my system is in /usr/lib/php5/20060613/. An easy way to find the PHP extension directory is to run:


ok, so I copied the to the extension directory:

sudo cp modules/ /usr/lib/php5/20060613/

So far so good. Now PHP needs to be told about the extension, and to load it. This can be done by adding


to the php.ini file. However, on my Ubuntu system, the PHP extensions are activated by adding an .ini file to the /etc/php5/apache2/conf.d directory, for each extension installed. The .ini file is the extension_name.ini, so I created a file called xdebug.ini:

cd /etc/php5/apache2/conf.d
gksu gedit xdebug.ini

which for now, contains a single line:


After restarting the Apache server

sudo /etc/init.d/apache2 restart

I created a file called test.php in my Web Root directory, containing a call to the phpinfo() function:


and pointed my browser to http://localhost/test.php. Just before the “PHP Credits” section, is a small box containing information on Zend – and now, with a successful Xdebug installation, additional information on Xdebug:

Xdebug information output by phpinfo()

The same information can be found by opening a Terminal and running

php -m

to output the loaded modules, and towards the end of the output, you should see

[Zend Modules]

alternatively, run

php -i | grep Xdebug

and if Xdebug has been installed successfully, you should see

with Xdebug v2.0.3, Copyright (c) 2002-2007, by Derick Rethans

Now, Xdebug needs to be enabled before any scripts can be debugged! So, in the php.ini file (or in my case, the newly created /etc/php5/apache2/conf.d/xdebug.ini file) I added the lines:


and restarted Apache again:

sudo /etc/init.d/apache2 restart


php -i | grep xdebug

in the Terminal, or using the test.php file containing phpinfo() shows that the new settings are being used, and Xdebug is active and running.

Configuring Eclipse PDT:

Setting up Eclipse PDT to use the Xdebug extension is pretty simple. In Eclipse PDT, I opened Window -> Preferences, then clicked on PHP, expanded the tree, and selected Debug. I Chose Xdebug from the pull down menu for the PHP Debugger, the “Default PHP Server” (should already be set to localhost), and then created a new PHP Executable option by clicking on the PHP Executables link next to the PHP Executable pull down menu.

XDebug and Eclipse PDT

In the PHP Executables dialog, I Clicked Add, filled in the name (PHP with XDebug), and entered the path to the PHP executable – on my system this is /usr/bin/php but if you don’t know, then in a terminal, run

which php

to find out where the php command is run from. I also entered the location of php.ini – again, on my system, this is /etc/php5/apache2/php.ini – and selected XDebug as the PHP debugger:

Xdebug - set up PHP Executable in Eclipse PDT

Clicked OK, then went back to the PHP -> Debug preferences screen, and selected the PHP Executable just created in the PHP Executable pull down. Finally, in the Debug -> Workbench Options option in the left, I selected “Never” for the “allow multiple debug sessions” option, since Xdebug does not support them.

Finally, I needed to set the Default Web Browser in Eclipse, to that when I debug a script, the output is sent to Firefox. Again in Preferences, I navigated to General -> Web Browser, and clicked “New”. It’s pretty straight forward stuff – entering a name and location – Firefox, and /usr/bin/firefox. Again, if you don’t know the location of the firefox binary, in a terminal run:

which firefox

With this done, and the preferences saved, I can now debug my scripts using Xdebug!

Using Xdebug in PDT


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