Quick WP Tip: Simple WordPress debugging


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17 August, 2010 – 28 Comments

After reading this post about the “WordPress white screen of death” I wanted to quickly share with you a quick hack I do in almost all WordPress installs I manage, that allows me to quickly switch on debug mode when needed.

In the file wp-config.php, usually found in your WordPress root, do the following:

if ( isset( $_GET['debug'] ) && 'debug' == $_GET['debug'] ) {
  define( 'WP_DEBUG', true );
  define( 'SCRIPT_DEBUG', true );

Now I can open any page, and if something goes wrong there, like a white screen of death, I add ?debug=debug to its URL and see what’s causing the trouble. Pretty easy huh? :)

Now it might be wise to change that second ‘debug’ to a key of your own choosing, so not everyone out there can open debug mode on your blog.

28 Responses

  1. digip
    By digip on 17 August, 2010

    Could you add that to functions.php?

  2. Steve
    By Steve on 17 August, 2010

    Brilliant! Sure could have used this before. Thanks Yoast!

  3. Ozh
    By Ozh on 17 August, 2010
  4. Leon
    By Leon on 17 August, 2010

    Thanks. And just in case anyone doesn’t realise how to change that second ‘debug’ to a key of your own choosing, it’s the third debug in the line of code above – “== ‘debug’)”

  5. nexik
    By nexik on 17 August, 2010

    It’s more secure to check if you are logged and have admin role. This way even if someone get your super secret key they won’t see anything until they are admins on the blog.

    global $current_user;
    if( isset( $_GET[ 'debug' ] ) && $_GET[ 'debug' ] == 'secret' && $current_user->user_level > 7  )
     define( 'WP_DEBUG', true );
  6. Theo
    By Theo on 17 August, 2010

    Great, useful as always, thanks ! @nexik – neat idea.

  7. Ozh
    By Ozh on 18 August, 2010

    @nexik: when WP loads wp-config.php, functions such as the one getting info for the current user are not loaded.

    The proper way to implement what you suggest is with a simple plugin:

    add_action( 'init', 'my_debug');
    function my_debug() {
       if( current_user_can('update_plugins')
           && isset( $_GET['debug'] )
           && $_GET['debug'] == 'secret'
           && !defined( 'WP_DEBUG' )
       ) { define( 'WP_DEBUG', true ); }

    (hope the comment formatting won’t crap out this)

    • Joost de Valk
      By Joost de Valk on 18 August, 2010

      The comment formatting actually makes it look great ;)

    • Cristian O. Balan
      By Cristian O. Balan on 25 August, 2010

      The Yoast suggestion on the wp-config file work fine but this code like a plugin don’t work. Some idea?

    • Andrew Nacin
      By Andrew Nacin on 28 August, 2010

      Unfortunately it’s too late here to define WP_DEBUG. Really, the only way to do this is to have a ‘secret’ as said.

      As long as you are logging WP_DEBUG instead of displaying it, you’re in better shape. Just don’t show them to the user.

  8. Pär Thernström
    By Pär Thernström on 18 August, 2010

    That’s so simple that it makes me angry that I did not think of it myself! :)
    Great tip, thanks.

  9. Tom Hermans
    By Tom Hermans on 18 August, 2010

    Yeah, this is pretty neat. Why didn’t I know about this when I was puzzled by al that WP code, functions etcetera.. giving me more whitescreens than my frustration could handle.. ;)

  10. Chris
    By Chris on 19 August, 2010

    Unfortunately I have the WSOD on the Dashboard and it doesn’t work there … I disabled the

    to avoid the WSOD, any ideas?

  11. Chris
    By Chris on 19 August, 2010

    ups … I meant

    >?php //wp_dashboard(); ?<

    • Chris
      By Chris on 19 August, 2010

      haha, stilt not quite … :-D

  12. Ron
    By Ron on 19 August, 2010

    Hi guys, im really a freaking noob here…hehe

    just one question though, can i just add the code directly to wp-config.php

    i was actually trying to have my blog on debug mode to check on something.,

    peace out

    • Joost de Valk
      By Joost de Valk on 19 August, 2010

      Yes. :)

      • Ron
        By Ron on 19 August, 2010

        wow, thanks for the quick reply..:)

        peace out

  13. Tailleur d'Images
    By Tailleur d'Images on 20 August, 2010

    hi !
    I’ve got a bug, but it doesn’t cause a white page, it create a big mess when I write a new post (i.e. it erases lines of text when i add a new line between 2 paragraphs, it put a whole paragraph in H2, asl…)

    so can i use this tip in order to fix it ? how ? i’ve been trying several things since now but it failed…

    thx for help !

  14. mike
    By mike on 27 August, 2010

    I copied/pasted both Yoost original code and nexik admin code in the wp-config.php file –
    and changed the third debug to my own secret word.
    (and tried with the original ?debug=debug too)

    but the only thing that happened was that the code-snippet was shown in the admin-page
    and in the pages on the blog. (on top of the page)
    and when pasting in the execution-snippet – nothing happens…
    is there something I am missing here…?



  15. Larry Swanson
    By Larry Swanson on 31 August, 2010

    I’m having the same problem as Mike, and I notice that the link to the debug=true for this page is no longer working (I saw it a week or so ago). Perhaps something changed in a WP release?

    • Joost de Valk
      By Joost de Valk on 31 August, 2010

      Yeah I disabled that on purpose :) has nothing to do with an upgrade :)