Remote PHP Debugging with Emacs

It’s an Emacs weekend here at blog.arithm.

I was recently asked if it was possible to do remote PHP debugging with Emacs. We’re talking about Emacs, so the answer is:  Of course!  How to do it:

  1. Grab Tohru Fujinaka’s GEBEN library.  It’s an aging alpha release, but works fairly well.
  2. Make sure you also have CEDET installed.  I’m using the 1.0 pre4 release.
  3. Drop debugclient somewhere in your path.  (Here Emacs is running on Windows, so I just threw it into the C:\WINDOWS\ directory.)  Make sure the executable is named “debugclient” and not “debugclient-0.9.0” or whatever.
  4. If you’re using the standard xdebug port 9,000 (recommended), make sure that port is open on your firewall.  For most folks these days that means opening up the default OS firewall as well as forwarding a port from the router.  See the exceptional portforward.com for more information on router port forwarding specifics.

Now, assuming you already have xdebug plugged into PHP, modify php.ini or an .htaccess file with the following settings:

  • xdebug.remote_enable = true
  • xdebug.remote_handler = dbgp
  • xdebug.remote_host = your_client_ip

For security reasons it’s wiser to do this via .htaccess on directories that permit only authenticated access.

To debug, ask Emacs to listen for connections by going into GEBEN Mode with Meta-x geben. You should see “xdebug started.” in the status row at the bottom of the Emacs window.

Run your PHP script with the xdebug switch on, eg.

http://www.example.com/script.php?XDEBUG_SESSION_START

If everything is setup correctly, Emacs will load the source of script.php (be wary of security!) and allow you to step through the code.

Available commands are:

spc step into/step over
i   step into
o   step over
r   step out
b   set a breakpoint at a line
u   unset a breakpoint at a line
g   run
q   stop

Some gotchas: I’ve noticed the GEBEN expects the first keystroke to be “space”; often it will freeze otherwise.  GEBEN may also run into problems on certain session-related PHP commands.

Happy debugging!

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