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Debugging PHP with Xdebug. Stephanie Russell Zachary Klink. Free and open source Swiss army knife for PHP developers. Developed by Derick Rethans Written in C Initial release date: May 2, 2002 Stable Release: 2.1.2 ; July 28, 2011. Xdebug. Stack and function traces in error messages
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Debugging PHP with Xdebug Stephanie Russell Zachary Klink
Free and open source Swiss army knife for PHP developers. • Developed by DerickRethans • Written in C • Initial release date: May 2, 2002 • Stable Release: 2.1.2; July 28, 2011 Xdebug
Stack and function traces in error messages • Full param display for user defined functions • Function name, file name and line number • Support for member functions • Memory allocation • Protection for infinite recursions • Profiling information for PHP scripts • Code coverage analysis • Debugger front-end to interactively debug Features
DBG • FirePHP • Gubed • PHP_Debug • MacGDBp Competition
Performance • Pause program execution • Usable with Eclipse, Netbeans, Notepad++, Chrome, Firefox, etc. Why Xdebug?
How to Xdebug Let’s dive a little deeper…
php.ini • When enabled, xdebug controls program execution. • As a server • GDB and DBGp • Remote control for PHP • Embedded into editor (no direct dealing with protocol itself) How to Xdebug
Modes: • Default: req. Makes xdebugalways connect to client when a script is started. • Second mode: jit. Only connect to the client on a breakpoint or error in script. • No setting in xdebug.remote_mode = default How to Xdebug
Negatives • Potential install/configuration nightmare • Compatibility issues Drawbacks
Internals How it works!
With remote debugging, embedded Xdebug in PHP acts as a client, and the IDE acts as a server. • The IP of the server is 10.0.1.2 with HTTP on port 80 • The IDE is on IP 10.0.1.42, so xdebug.remote_host is set to 10.0.1.42 • The IDE listens on port 9000, so xdebug.remote_port is set to 9000 • The HTTP request is started on the machine running the IDE • Xdebug connects to 10.0.1.42:9000 • Debugging runs, HTTP Response provided Internals – single dev
Setup is only slightly different: • The IP of the server is 10.0.1.2 with HTTP on port 80 • The IDE is on an unknown IP, so xdebug.remote_connect_back is set to 1 • The IDE listens on port 9000, so xdebug.remote_port is set to 9000 • The HTTP request is made, Xdebug detects the IP address from the HTTP headers • Xdebug connects to the detected IP (10.0.1.42) on port 9000 • Debugging runs, HTTP Response provided Internals – multiple dev
Tracks debug session through brower: cookies • URL variable XDEBUG_SESSION_START=name appended to URL • Xdebug emits cookie with name “XDEBUG_SESSION” with value “name.” • This expires in an hour. • DBGp protocol also passes this value to the init packet when connecting to debug client Internals – Debug session
When there is a GET or POST, the cookie is set, xdebug connects to a debug client. • To stop debug session (and destroy the cookie), add URL parameter XDEBUG_SESSION_STOP. • Xdebug not longer tries to connect to debug client. Internals – Debug session
Can specify one IP or multiple users • xdebug.remote_host or • If IP not known: xdebug.remote_connect_back Internals – Multiple Users
Installation Be sure to wear your helmet.
PHP 5 • Apache2 First
Apt-get • Compatibility with PHP release • Find installed xdebug.so • Edit php.ini file to add zend extension. • Remote host/port • Known IP (edit 09/22 or for multiple developers) • Port open Install
Netbeans Tools > Options > PHP • Set debug port = remote_port Integrate with Netbeans
Demo Valiantly attempting to avoid Murphy’s law
Resources Research is key to success
http://www.firephp.org/HQ/Use.htm • http://sixrevisions.com/web-development/how-to-debug-php-using-firefox-with-firephp/ • http://www.php-debugger.com/dbg/ • http://gubed.mccabe.nu/ • http://coding.smashingmagazine.com/2009/01/20/50-extremely-useful-php-tools/ • http://www.bluestatic.org/software/macgdbp/ Competition Resources
http://xdebug.org/docs/remote • http://ubuntuforums.org/showthread.php?t=525257 • http://scottfaisal.com/installing-xdebug-on-ubuntu-10-04/ • http://2bits.com/articles/setting-up-xdebug-dbgp-for-php-on-debian-ubuntu.html • http://netbeans.org/kb/docs/php/configure-php-environment-ubuntu.html • http://wiki.netbeans.org/HowToConfigureXDebug • http://stackoverflow.com/questions/693074/how-to-debug-php-with-netbeans-and-xdebug • http://blogs.oracle.com/netbeansphp/entry/howto_check_xdebug_installation Installation Resources
http://xdebug.org Everything Else Resources