Title: [Plugin: Appointment Calendar] Warning: Cannot modify header information Last modified: August 20, 2016 --- # [Plugin: Appointment Calendar] Warning: Cannot modify header information * [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/) * I get this error, when I try to add [APCAL] to a page * Warning: Cannot modify header information – headers already sent by (output started at /home/content/g/e/o/geofferson/html/promediate/wp-content/plugins/appointment- calendar/calendar_shortcode.php:1829) in /home/content/g/e/o/geofferson/html/ promediate/wp-includes/pluggable.php on line 866 * Any advice? * [http://wordpress.org/extend/plugins/appointment-calendar/](http://wordpress.org/extend/plugins/appointment-calendar/) Viewing 15 replies - 1 through 15 (of 28 total) 1 [2](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/page/2/?output_format=md) [→](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/page/2/?output_format=md) * Plugin Contributor [FARAZFRANK](https://wordpress.org/support/users/farazfrank/) * (@farazfrank) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497368) * Hi Geofferson, we got your problem may be some extra php-tags or blank space on that line soon we will reduce this bug n inform you with new update Thank you !!! * Plugin Author [a.ankit](https://wordpress.org/support/users/aankit/) * (@aankit) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497512) * Hi Geofferson, * We have updated the plugin. Could you check if it now works on your system. * -Ankit * Thread Starter [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497515) * When I tried to re-activate the plugin, this notice appeared at the top… * The plugin generated 4 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin. * Plugin Author [a.ankit](https://wordpress.org/support/users/aankit/) * (@aankit) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497535) * Hmmm.. are you able to add [APCAL] now on your page? * [opsec](https://wordpress.org/support/users/opsec/) * (@opsec) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497657) * I’m getting that error too on a fresh install. * “plugin generated 4 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.” * also, is it possible to delete bookings in the “booking management” section, I wanted to delete my tests and I can’t find a delete feature anywhere. * Thanks * Plugin Contributor [FARAZFRANK](https://wordpress.org/support/users/farazfrank/) * (@farazfrank) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497661) * Hi opsec, Yes, its possible to delete appointment in booking management. A filter button above the table. You need to filter your appointment by ‘pending’ and change its status ‘canceled’. then filter again by ‘canceled’ and checked those appointments you want to delete, and hit the delete button. * and above error not a critical issue, we will refine this bug in next version. * Thank You !!! * Thread Starter [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 5 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497665) * I tried to re-install the plugin and got this message * “The plugin generated 2 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.” * Plugin Author [a.ankit](https://wordpress.org/support/users/aankit/) * (@aankit) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497671) * [@opsec](https://wordpress.org/support/users/opsec/): Were you able to delete the bookings?? * [@geofferson](https://wordpress.org/support/users/geofferson/): The extra character error is not a critical bug, it would be fixed in upcoming versions.. by the way were you able to use all the features of appointment calendar? * Thread Starter [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497680) * It seems to be working, does this look right? * [http://www.promediate.ca/calendar-booking/](http://www.promediate.ca/calendar-booking/) * Thread Starter [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497686) * What if you don’t want to publicly show the names of people booking appointments, but just that the time slot is unavailable, any way to do this? * Plugin Author [a.ankit](https://wordpress.org/support/users/aankit/) * (@aankit) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497696) * [@geofferson](https://wordpress.org/support/users/geofferson/) .. – Yeah it seems to be working fine. * – In future version we will remove client’s name from the booking calendar. * -Ankit * Thread Starter [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497697) * Removing client’s name from the public calendar is key if I’m going to keep using this plugin. * Also, I haven’t tested this yet, but when an appointment is approved or changed, is an email confirmation sent to the appointee? * Plugin Author [a.ankit](https://wordpress.org/support/users/aankit/) * (@aankit) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497703) * Notification are not included in the current version.. however email notifications will be supported in Version 1.0 * Thread Starter [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497704) * Sounds good, thanks for the quick responses. when is V 1.0 expected to release? * Thread Starter [geofferson](https://wordpress.org/support/users/geofferson/) * (@geofferson) * [14 years, 4 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/#post-2497705) * Just adding that it would be good to have a better method to delete bookings, thanks. Viewing 15 replies - 1 through 15 (of 28 total) 1 [2](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/page/2/?output_format=md) [→](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/page/2/?output_format=md) The topic ‘[Plugin: Appointment Calendar] Warning: Cannot modify header information’ is closed to new replies. * ![](https://s.w.org/plugins/geopattern-icon/appointment-calendar.svg) * [Appointment Calendar](https://wordpress.org/plugins/appointment-calendar/) * [Frequently Asked Questions](https://wordpress.org/plugins/appointment-calendar/#faq) * [Support Threads](https://wordpress.org/support/plugin/appointment-calendar/) * [Active Topics](https://wordpress.org/support/plugin/appointment-calendar/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/appointment-calendar/unresolved/) * [Reviews](https://wordpress.org/support/plugin/appointment-calendar/reviews/) * 28 replies * 4 participants * Last reply from: [FARAZFRANK](https://wordpress.org/support/users/farazfrank/) * Last activity: [13 years, 7 months ago](https://wordpress.org/support/topic/plugin-appointment-calendar-warning-cannot-modify-header-information/page/2/#post-2497854) * Status: not resolved