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I am trying to create a debugging mode in one of my plugins so users can easily enable WP_DEBUG on their own, and hopefully report back to us with helpful error messages. Right now we ask them to modify their wp-config.php, but that's beyond some users' capabilities. I was hoping to just add define( 'WP_DEBUG', true );in our plugin if the user has checked that option, but it appears you can only enable WP_DEBUG from the wp-config.php file.

Does anyone know of any way to enable WP_DEBUG from anywhere else but wp-config? Or is there another useful WP function that I could be using instead?

Thanks, Dalton

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Guess what, I tried the exact same thing a couple of days back, but didn't work. And if there was a way, then an option to turn on/off the debug mode via the dashboard would've been there cause editing the config is very risky! Anyways you can try this way: wordpressluv.com/… – Rutwick Gangurde Mar 28 '12 at 12:12
Thanks Rutwick, that link is super helpful. Won't work for me in this case (I need to be able to display errors without editing wp-config.php) but I can see this coming in very handy. – Dalton Mar 28 '12 at 13:52
You're welcome @Dalton! If you find a way, please let me know too! – Rutwick Gangurde Mar 28 '12 at 14:30
up vote 4 down vote accepted

WordPress logic forces WP_DEBUG to be defined to something, even if it's omitted it will be set to false in wp_initial_constants() during load.

However "background" (that is not when it is checked explicitly) function of WP_DEBUG is to be a flag for how PHP error reporting should be configured on runtime. That configuration is performed by wp_debug_mode() and at any point after that can be changed by your plugin's code if necessary.

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Thanks for that background info, I did not know about wp_debug_mode(). Even when changed after the fact, it still cannot override the initial setting of WP_DEBUG in the wp-config, can it? – Dalton Mar 28 '12 at 13:51
@Dalton correct, you can't change constant itself, but you can easily change error reporting settings. – Rarst Mar 28 '12 at 14:06

It is not possible to turn on WP_DEBUG because it's defined in wp-config.php by default, redefinition of defined constants is not possible in PHP.

If you want to keep them out of wp-config.php ask them to add to the top something like:

if ( file_exists( 'safe-wp-config.php' ) ) {
    /* this will contains WP_DEBUG */
    include 'safe-wp-config.php';


WP_DEBUG is assumed to be false when missing, so let them remove WP_DEBUG completely from wp-config.php and use wherever/whenever they like.

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it's possible with runkit – onetrickpony Mar 28 '12 at 13:27
@onetrickpony Thanks for the tip but I need some advice. Why wouldn't something along these lines work (added in my theme's functions.php)? runkit_constant_redefine( 'WP_DEBUG' , true ); runkit_constant_add( 'WP_DEBUG_LOG', true ); runkit_constant_add( 'WP_DEBUG_DISPLAY', true ); – Henrik Mar 26 '14 at 16:26

However, if you really want to display errors and not store them in log file (like I wanted), then you can turn on debugging for your Public IP like following -

if ( $_SERVER['REMOTE_ADDR'] == 'xxx.xxx.xxx.xxx')
define('WP_DEBUG', true);

There should not be a problem as long as you are on Static IP, but if you have dynamic IP, you probably can change the IP every time you need to turn on debugigng.

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