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Komodo 4.4 Documentation

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Debugging PHP Komodo IDE only

Tutorial

Komodo can be used to debug PHP programs locally or remotely. Remote PHP debugging encompasses all types of PHP debugging not initiated from within Komodo, including debugging PHP scripts running under a local web server.

The instructions below describe how to configure Komodo and PHP for debugging. For general information about using the Komodo debugger, see Komodo Debugger Functions.

Debugger commands can be accessed from the Debug menu, by shortcut keys, or from the Debug Toolbar. For a summary of debugger commands, see the Debugger Command List.

Komodo uses a PHP debugger extension called Xdebug that must be installed for Komodo to debug PHP scripts. This can be done manually or with the PHP Configuration Wizard. Pre-built binaries named "php_xdebug.dll" (for Windows) or "xdebug.so" (for Linux and Mac OS X) are provided with Komodo and are also available for download from the Komodo Remote Debugging page.

See www.xdebug.org/install.php for instructions on compiling Xdebug from source on other platforms.

Installing PHP

PHP debugging in Komodo will work with PHP 4.3.11 or later, with the exception of versions 5.0.0 through 5.0.2. If you are using PHP 5.0, you will need at least 5.0.3 or greater. Download PHP from http://www.php.net/downloads.php.

Refer to the PHP website for detailed information on installing PHP.

To debug PHP scripts in a web environment, be sure PHP is operating correctly with your web server before configuring the debugger extension. Consult the PHP documentation for details on configuring PHP with various web servers.

Windows

If you are unfamiliar with the installation of PHP, we recommend using the Windows InstallShield package. To install the PHP executable or SAPI module manually, see the PHP website. Be sure that the PHP directory is included in your system's PATH.

Linux

Your Linux system may already have PHP installed. Login and type 'php -v' to determine the version of your current PHP interpreter. If it is earlier than version 4.3.11 (or 5.0.0 through 5.0.2) you must upgrade. PHP must also support loading dynamic extensions (the default for PHP under Linux). If it does not, reinstall PHP as per the instructions on the PHP website.

When installing PHP to a non-default directory, you must add the following argument to the ./configure command:

--with-config-file-path=/path/to/php.ini

where /path/to/php.ini is the full path to the directory where the php.ini file is located.

Mac OS X

Although both the Jaguar and Tiger releases of OS X include a version of PHP, it is recommended that you obtain a more recent version. Either build from source code, or download a PHP module for OS X's Apache web server from www.entropy.ch/software/macosx/php/.

Local PHP Debugging

In local debugging mode, Komodo executes PHP directly. While this is convenient for quickly debugging a PHP script, if your script depends on the availability of a web server, use Remote PHP Debugging even if the script is running on the same machine as Komodo. This makes it possible to test the script in its true environment.

When debugging locally, certain environment variables are not available, such as those provided by the CGI environment. However, it is possible to simulate a CGI environment by specifying CGI environment variables and CGI input in the Debugging Options dialog box. It is is not necessary to install a web server to use Komodo's local debugging features. Once you have configured PHP to use the debugger extension as described below, you can debug your scripts by opening a PHP file and using Komodo Debugger Functions.

If you receive an error message when attempting to debug a PHP script, check the PHP troubleshooting section of the Komodo FAQ.

Configuring Local PHP Debugging

Komodo configures itself automatically for local PHP debugging by launching the default PHP interpreter (i.e. the first in your PATH) and attempting to load the Xdebug extension (php_xdebug.dll or xdebug.so). If this is successful, a new copy of php.ini is created automatically with debugging enabled which Komodo will use when debugging PHP scripts locally.

PHP Debugger Config Wizard

If the automatic configuration of PHP debugging is not successful, try configuring PHP debugging manually using the PHP Configuration Wizard.

To start the wizard:

  1. On the Edit menu, click Preferences.
  2. Under Languages, select PHP.
  3. Click the Debugger Configuration Wizard button to display the wizard's introductory window.
  4. Click Next to begin configuring PHP for debugging.

The wizard will guide you through the steps necessary to configure the debugging extension.

  1. Choose Installation:

    The first step assumes that you have already installed PHP. If you have more than one version of PHP installed, choose the version to configure. Browse to the directory containing the PHP executable or enter the directory path in the Set up this installation field, and then click Next.

  2. Choose PHP INI Path:

    Next, choose the php.ini file to be copied and its destination directory. Subsequent changes to the original file will not be available in the new copy. Modify the new file directly, or rerun the wizard to copy the changes. Click Next.

    • On Windows, the php.ini file is generally located in c:\windows, or c:\winnt, depending on your operating system. It may also be located in the same directory as your php.exe executable.
    • On Linux, the default location is /usr/local/lib. It may also be located in the same directory as your PHP executable.

  3. Choose PHP Extension Directory:

    Many PHP installations already include a default "extensions" directory. This is where the debugger extension should be installed. If you have specified an extensions directory in the .ini file, you do not need to change the path that appears in the Use this extensions directory field. It is important that the extensions are installed in the same directory as your PHP installation. If you choose a different location, some extensions may not work. Once the desired path is set, click Next.

  4. Ready to Install:

    The final window in the wizard displays the installation options. Confirm that the selections are correct and click Next. To change any of the selections, click Back.

The PHP Configuration Wizard is only used to configure local debugging. To debug PHP remotely on a web server, see Configuring Remote PHP Debugging.

If the wizard does not successfully enable local PHP debugging, refer to Configuring Remote PHP Debugging for more information on manual configuration and Common PHP Debugging Problems for information on common problems.

Starting and Stopping a PHP Local Debugging Session

To step through the script, from Debug menu, select Step In.

To run the script to the first breakpoint, from the Debug menu, select Go/Continue.

To stop the debugger, from the Debug menu, select Stop.

See Komodo Debugger Functions for full instructions on using Komodo's debugging functionality.

Remote PHP Debugging

Remote PHP debugging encompasses all types of PHP debugging not initiated from within Komodo, including debugging PHP scripts running under a local web server.

When a PHP script is run through a web browser, the web server uses the PHP interpreter to execute the script. If PHP is configured for remote debugging, the server contacts Komodo to start a debugging session. Komodo controls the debugging (e.g. stepping and breakpoints) once the session starts. CGI variables are available, as are all other variables that are available when running PHP under a web server.

Though remote PHP debugging allows PHP scripts to be run in their true environment, it may be slower than local PHP debugging.

Configuring Remote PHP Debugging

Remote debugging of PHP in Komodo is set up differently depending on how many people will be debugging scripts on the same web server:

Single User Remote PHP Debugging: In single user remote debugging, PHP is configured to always look for a specific instance of Komodo on a specific machine. This configuration requires no changes to the PHP script. Your web server and your instance of Komodo can be on one machine or two machines

Multi-User Remote PHP Debugging: When multiple users need to debug PHP scripts on a single web server, use the DBGP Proxy with the remote PHP debugging instructions below. While it is possible to configure Apache with Virtual Hosting, it is easier to configure multi-user remote PHP debugging with the proxy.

Remote PHP debugging must be configured manually. The following procedure assumes that you have already installed PHP.

Step 1 - Copy the Debugging Extension to the Web Server

Before debugging PHP scripts in Komodo, PHP must be configured to use the Xdebug extension (php_xdebug.dll or xdebug.so).

Find the appropriate extension for the version of PHP you are running and manually copy it into a directory on the server that the PHP interpreter and web server can access. The Xdebug files can be found in the php sub-directory of the Komodo installation. For example:

Windows

  • File: php_xdebug.dll
  • Location: <komodo-install-directory>\lib\support\php\debugging\<PHP-version> or the Komodo Remote Debugging page.

Linux

  • File: xdebug.so
  • Location: <komodo-install-directory>/lib/support/php/debugging/<PHP-version>/ or the Komodo Remote Debugging page.

Mac OS X

  • File: xdebug.so
  • Location: <komodo-install-directory>/Contents/SharedSupport/lib/support/php/debugging/<PHP-version>/ or the Komodo Remote Debugging page.

In the downloadable packages, the extensions are found in version-specific subdirectories of the unpacked archive.

The Xdebug extension does not have to be installed in the PHP extension_dir because it's location is specified explicitly in php.ini (see below).

Step 2 - Edit the Web Server's PHP Configuration

Open the php.ini configuration file on the web server. In the "Dynamic Extension" section, add the lines specified below. Edit the values to reflect your particular environment (see Xdebug settings explained below).

Note: Xdebug is incompatible with the Zend Optimizer and Zend Studio Debugger extensions. These extensions should be commented out in php.ini when configuring PHP for remote debugging with Komodo.

  • Windows

    The php.ini configuration file should be in your operating system directory (e.g. C:\WINDOWS or C:\WINNT), or in the same directory as php.exe (e.g. C:\PHP). If you used the PHP Windows installer, this file should be in the correct location.

    ; xdebug config for Windows
    zend_extension_ts=c:\path\to\php_xdebug.dll
    xdebug.remote_enable=1
    xdebug.remote_handler=dbgp
    xdebug.remote_mode=req
    xdebug.remote_host=127.0.0.1
    xdebug.remote_port=9000
    xdebug.idekey=<idekey>
    
  • Linux and Mac OS X

    ; xdebug config for Linux and Mac OS X
    zend_extension=/path/to/xdebug.so
    xdebug.remote_enable=1
    xdebug.remote_handler=dbgp
    xdebug.remote_mode=req
    xdebug.remote_host=127.0.0.1
    xdebug.remote_port=9000
    xdebug.idekey=<idekey>
    

Xdebug settings explained:

zend_extension_ts or zend_extension
Should be set to the full path to the xdebug library on your system. Use zend_extension_ts ("thread safe") on Windows and zend_extension on other platforms.
xdebug.remote_enable
Enables remote debugging.
xdebug.remote_handler
Should be set to dbgp for use with Komodo.
xdebug.remote_mode
Set to req to have the script connect to Komodo when it starts. Set to jit to connect only on an error condition (see PHP Just-in-Time Debugging / Break on Exception).
xdebug.remote_host
Set to the hostname or IP address of the computer running Komodo or the DBGP Proxy. Use 'localhost' or '127.0.0.1' if Komodo and the web server are running on the same system.
xdebug.remote_port
Set to the same value as the debugging listener port configured in the Debugger Connection preferences (or the system assigned Host Port displayed under Debug|Listener Status)
xdebug.idekey (optional)
If you are using the DBGP Proxy, set this to the Proxy Key configured in the Debugger Connection preferences.

Restart the web server to load the new configuration.

Step 3 - Verify the Web Server's PHP Configuration

Once the php.ini file is updated, verify that Xdebug is configured by running the following command:

php -m

If your command-line PHP interpreter uses a different php.ini file (this is often the case) or if you're not sure which file it uses, create a phpinfo.php file containing the line '<?php phpinfo(); ?>' in a web server directory to display the configuration in a web browser.

Make sure Xdebug appears in the Zend module lists, but not in the PHP module list.

Note: Recent versions of PHP are set to buffer program output by default. While debugging, it is useful to disable output buffering so that results of print and echo statements can be seen immediately when stepping through code. To disable output buffering, comment out the output_buffering setting in php.ini with a ";" character, or set it to "off".

Starting and Stopping a PHP Remote Debugging Session

Once remote PHP debugging is configured, the PHP interpreter can contact Komodo and initiate a remote debugging session when a PHP script is executed on the web server.

To initiate remote debugging from a web browser:

  1. Ensure PHP is installed and configured properly for your web server.
  2. Ensure Komodo and PHP are configured for remote debugging (as described in "Configuring Remote PHP Debugging").
  3. Click Debug | Listen for Debugger Connections.
  4. In your browser, enter the URL of the script you want to debug. Append ?XDEBUG_SESSION_START=1 to the end of the URL (an HTTP GET with a true boolean value). For example:
    http://example.org/sample.php?XDEBUG_SESSION_START=1
    
    If you are using the DBGP Proxy, the value for the GET method should match the Proxy Key value shown in Debug|Listener Status. For example:
    http://example.org/sample.php?XDEBUG_SESSION_START=jdoe 
    It is also possible to call XDEBUG_SESSION_START by adding it in an input element of an HTML form. For example:
    <input type="hidden" name="XDEBUG_SESSION_START" value="jdoe" />
    

    Note: This is only required for the first request. After that, Xdebug tracks the debugging session with a cookie. For more information on how this works, see www.xdebug.org/docs-debugger.php#browser_session

  5. A PHP debugging session starts in Komodo. On the Debug menu, click Step In or Go/Continue to run to the first breakpoint.

To initiate remote debugging from the command line:

  1. On the Debug menu, click Listen for Debugger Connections.
  2. Set the XDEBUG_CONFIG environment variable. Use the port specified in Edit|Preferences|Debugger or listed in Debug|Listener Status.

    On Windows:
    set XDEBUG_CONFIG=remote_port=9000 remote_enable=1
    
    On Linux/Mac OS X:
    export XDEBUG_CONFIG="remote_port=9000 remote_enable=1"
    

  3. Run the script using the PHP interpreter:
    php -f sample.php
    
  4. A PHP debugging session will start in Komodo. Click Step In to start stepping through the script or Go/Continue to run to the first breakpoint.

To initiate remote debugging using the DBGP Proxy:

  1. From the Debug menu, select Listen for Debugger Connections.
  2. Set the XDEBUG_CONFIG environment variable as above. Use the port specified in Edit|Preferences|Debugger or listed in Debug|Listener Status. Add an IDE Key value to the XDEBUG_CONFIG environment variable that matches the Proxy Key value shown in Debug|Listener Status.

    On Windows:
    $set XDEBUG_CONFIG=remote_port=9000 remote_enable=1 idekey=<USERNAME>
    
    On Linux/Mac OS X:
    export XDEBUG_CONFIG="remote_port=9000 remote_enable=1 idekey=<USER>"
    
  3. Run the script using the PHP interpreter:
    php -f sample.php
    
  4. A PHP debugging session will start in Komodo. On the Debug menu, Click Step In to start stepping through the script or Go/Continue to run to the first breakpoint.

Output from the debug session appears in the Bottom Pane of the Komodo Workspace. Komodo does not support a console for remote debugging. The browser will not show the script output until debugging is complete.

To stop the debugger:

On the Debug menu, select Stop or pass the XDEBUG_SESSION_STOP=1 variable by appending it to the URL or adding it to a form (as with XDEBUG_SESSION_START=1 above).

See Komodo Debugger Functions for full instructions on using Komodo's debugging functionality.

If you receive an error message while debugging a PHP script that is not caused by the errors in the script itself, check the PHP troubleshooting section of the Komodo FAQ.

Using xdebug_break()

The xdebug_break() function is used to hard-code a break in a PHP program. It can be used instead of a Komodo breakpoint. For example:

<?php
echo "<p>Breaks after this line.</p>";
xdebug_break();
echo "<p>Breaks before this line.<p>";
?>

This function breaks the code during a debugging session but will not initiate a new session. Use xdebug_break() in conjunction with the methods described above for starting debugging sessions.

Xdebug Logging

To log xdebug sessions on the server, add the following line to the xdebug config section of the php.ini configuration file:

xdebug.remote_log=/tmp/xdebug.log

...or add remote_log to the XDEBUG_CONFIG environment variable. For example:

export XDEBUG_CONFIG="remote_port=9000 remote_enable=1 remote_log=/tmp/xdebug.org"

You can replace "/tmp/xdebug.org" with any writable directory and the filename of your choice.

PHP Just-in-Time Debugging / Break on Exception

PHP remote debugging can be configured to break when an exception is thrown. Sometimes called just-in-time debugging, this method allows you to test your application and stop to examine code when there is a problem.

To turn this on, change the xdebug.remote_mode setting in php.ini from 'req' to 'jit' or override the setting in your code:

<?php 
ini_set('xdebug.remote_mode', 'jit');
...
?>

Whenever an exception is thrown, a debugging session is initiated with a break at the line that caused the problem.

This may generate a lot of breaks if PHP is configured with verbose error handling (e.g. error_reporting = E_ALL). In PHP 5, you can define your own Exception class which enables JIT debugging only for specific exceptions:

<?php
class KoException extends Exception
{
  function __construct($message, $code = 0) {
    ini_set('xdebug.remote_mode', 'jit');
    parent::__construct($message, $code);
  }
}

throw new KoException('this is my exception!', 42);
?>

Common PHP Debugging Problems

Debugging PHP on OS X

The version of PHP supplied with Mac OS X is not complied with loadable extension support, so it is not compatible with Komodo's debugger (Xdebug). For PHP debugging on OS X, either build PHP from source with loadable extension support or use binaries from http://www.entropy.ch/software/macosx/php/. The 4.3.11 or 5.0.4 for Apache 1 packages have been found to work well with Komodo PHP debugging.

Debugging PHP on 64-bit Linux

The version of xdebug.so for Linux provided by Komodo is not compatible with 64-bit versions of PHP. To configure PHP debugging on 64-bit Linux systems, compile Xdebug from source, replace Komodo-<version>/lib/support/php/debugging/<PHP version>/xdebug.so with the new 64-bit version, and run the PHP Configuration Wizard.

Zend Optimizer and Zend Studio Debugger

Xdebug is incompatible with the Zend Optimizer and Zend Studio Debugger extensions. If these extensions are enabled in php.ini, they will not be imported into the copy created by Komodo for debugging. When configuring Remote PHP Debugging, these extensions should be manually commented out in php.ini.