Title: Debug mode headers already sent Last modified: August 21, 2016 --- # Debug mode headers already sent * [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/) * Hi, when DEBUG is true, I get white screen and these warnings when trying to save a Post or Page… * ``` Notice: Undefined offset: 0 in /public_html/wp-includes/capabilities.php on line 1102 Warning: Cannot modify header information - headers already sent by (output started at /public_html/wp-includes/capabilities.php:1102) in /public_html/wp-admin/post.php on line 235 Warning: Cannot modify header information - headers already sent by (output started at /public_html/wp-includes/capabilities.php:1102) in /public_html/wp-includes/pluggable.php ``` * Plugins we use have to pass debug mode :-/ * Thanks for any help! * [https://wordpress.org/plugins/contextual-related-posts/](https://wordpress.org/plugins/contextual-related-posts/) Viewing 11 replies - 1 through 11 (of 11 total) * Plugin Author [Ajay](https://wordpress.org/support/users/ajay/) * (@ajay) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963618) * Why do you think this is a problem with Contextual Related Posts. Is there a way for me to replicate this? * I test my plugins with WP_DEBUG set to true * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963627) * (see below) * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963628) * ** Maybe it’s the META BOX ??? * Here are the steps to replicate… * 1. DEBUG is true 2. MultiSite is true 3. All plugins deactivated 4. Twentyfourteen theme only 5. Activate CRP plugin 6. Create and Save a “test” post * Get white screen and notices above. * I have repeated steps with popular plugins like CF7, EMP, etc. This seems to happening with Contextual Related Posts. * *** I have not tried with WP clean install or single blog. I have only tried with the steps listed above on MultiSite only. * localhost WP 3.9.1 MultiSite PHP 5.4.4 * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963629) * OK, it appears to be the meta box as assumed. I am currently debugging now. I have currently disabled the meta box: * **admin.inc.php (760)** * ``` function crp_add_meta_box( $post_type, $post ) { add_meta_box( 'crp_metabox', __( 'Contextual Related Posts', CRP_LOCAL_NAME ), 'crp_call_meta_box', $post_type, 'advanced', 'default' ); } //add_action( 'add_meta_boxes', 'crp_add_meta_box' , 10, 2 ); ``` * When I disable meta box, I can easily save a post. * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963630) * Line 773, admin.inc.php * `wp_nonce_field( 'crp_meta_box', 'crp_meta_box_nonce' );` * Commenting out the nonce solves the problem. I will investigate further… * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963631) * Maybe it’s a caching problem? I cannot verify nonce 🙁 * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963632) * Okay, it’s NOT the nonce. It’s user roles. I should’ve know (because capabilities. php warning): ** admin.inc.php (809) * `if ( ! current_user_can( 'edit_post' ) ) return;` * I am done debugging. I’m just going to comment out that line and figure it out later. FYI, there are returns with no error handlers. Also, textdomain’s should not use DEFINED vars 😉 * Cool plugin, thanks! * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963634) * I’m going to add this for now…what do you think? * ``` if ( isset( $_POST['crp_meta_box_nonce'] ) ) { if ( ! current_user_can( 'edit_post', $post_id ) ) { return; } } ``` * Plugin Author [Ajay](https://wordpress.org/support/users/ajay/) * (@ajay) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963639) * Hi, * Thanks for the detailed debugging steps. I followed the tutorial at [http://code.tutsplus.com/tutorials/how-to-create-custom-wordpress-writemeta-boxes–wp-20336](http://code.tutsplus.com/tutorials/how-to-create-custom-wordpress-writemeta-boxes–wp-20336) with these steps. * Does your code above work or have you disabled the nonce ? * I’m wondering if the problem is with multisite because although the plugin works with multisite, I don’t think it is 100% compatible. * Thread Starter [sem101](https://wordpress.org/support/users/sem101/) * (@sem101) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963642) * Hi Ajay, * So far, seems to work great WITHOUT removing nonce. I see you have 2 nonces in your form, but haven’t looked at all code so I don’t know reference. * This seems to be most non intrusive code that does not modify anything greatly. Hope it helps! * ``` if ( isset( $_POST['crp_meta_box_nonce'] ) ) { if ( ! current_user_can( 'edit_post', $post_id ) ) { return; } } ``` * Plugin Author [Ajay](https://wordpress.org/support/users/ajay/) * (@ajay) * [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963643) * Thank you. I’ll relook at the code and add what you’ve put and run some tests. Viewing 11 replies - 1 through 11 (of 11 total) The topic ‘Debug mode headers already sent’ is closed to new replies. * ![](https://ps.w.org/contextual-related-posts/assets/icon-256x256.png?rev=2985705) * [Contextual Related Posts](https://wordpress.org/plugins/contextual-related-posts/) * [Frequently Asked Questions](https://wordpress.org/plugins/contextual-related-posts/#faq) * [Support Threads](https://wordpress.org/support/plugin/contextual-related-posts/) * [Active Topics](https://wordpress.org/support/plugin/contextual-related-posts/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/contextual-related-posts/unresolved/) * [Reviews](https://wordpress.org/support/plugin/contextual-related-posts/reviews/) ## Tags * [headers](https://wordpress.org/support/topic-tag/headers/) * 11 replies * 2 participants * Last reply from: [Ajay](https://wordpress.org/support/users/ajay/) * Last activity: [12 years ago](https://wordpress.org/support/topic/debug-mode-headers-already-sent/#post-4963643) * Status: not resolved