Title: Call Back Functions & Header Modify Errors Last modified: August 30, 2016 --- # Call Back Functions & Header Modify Errors * Resolved [ty5280](https://wordpress.org/support/users/ty5280/) * (@ty5280) * [10 years, 9 months ago](https://wordpress.org/support/topic/call-back-functions-header-modify-errors/) * I have been using this plugin for months…starting today in both my prod and test instances I get the following when attempting to approve/deny users. * I tried deactivating/re-activating…that did not clear the issue. * ‘[https://mysite.com/wp-admin/users.php?action=approve&user=35&_wpnonce=4ce4fe07ad](https://mysite.com/wp-admin/users.php?action=approve&user=35&_wpnonce=4ce4fe07ad) * Warning: call_user_func_array() expects parameter 1 to be a valid callback, function‘ set_html_content_type’ not found or invalid function name in /home/mysite/public_html/ wp-includes/plugin.php on line 213 * Warning: call_user_func_array() expects parameter 1 to be a valid callback, function‘ set_html_content_type’ not found or invalid function name in /home/mysite/public_html/ wp-includes/plugin.php on line 213 * Warning: Cannot modify header information – headers already sent by (output started at /home/mysite/public_html/wp-includes/plugin.php:213) in /home/mysite/public_html/ wp-includes/pluggable.php on line 1207′ * [https://wordpress.org/plugins/new-user-approve/](https://wordpress.org/plugins/new-user-approve/) Viewing 3 replies - 1 through 3 (of 3 total) * Thread Starter [ty5280](https://wordpress.org/support/users/ty5280/) * (@ty5280) * [10 years, 9 months ago](https://wordpress.org/support/topic/call-back-functions-header-modify-errors/#post-6526238) * Interesting development. I restored a copy of the site from the production HostGator VPS to a different hosting providers VPS on my dev VPS and the issue is not happening on my dev VPS. * This error was not happening until today on prod VPS…so what should I be talking to HostGator support about with regards to config changes on the server that would cause this? * Thread Starter [ty5280](https://wordpress.org/support/users/ty5280/) * (@ty5280) * [10 years, 9 months ago](https://wordpress.org/support/topic/call-back-functions-header-modify-errors/#post-6526393) * So HG escalated issue to their sys admin and their response is below. * This does not explain why all of a sudden the plugin is not working when I have been using the plugin for 90+ days and it was working the WP Core 4.3 for nearly 3 weeks…with the issue just happening in the past few days. * This also does not explain why when I do a clone backup using Duplicator and restore it on another VPS that is not hosted by HG the plugin works just fine. * However, I do think HG’s response warrants review by the plugin developer: * Turning on WordPress debug mode,shows a number of other errors. When I enabled WordPress debugging mode, the site appears with these errors: * Notice: The called constructor method for WP_Widget is deprecated since version 4.3.0! Use * __construct() * instead. in /home/mysite/public_html/wp-includes/functions.php on line 3457 * Warning: Cannot modify header information – headers already sent by (output started at /home/mysite/public_html/wp-includes/functions.php:3457) in /home/mysite/public_html/ wp-includes/pluggable.php on line 1207 * This points to an incompatible plugin. You’ll want to make sure all your plugins are compatible with WordPress 4.3. Looking at [https://wordpress.org/plugins/new-user-approve/faq/](https://wordpress.org/plugins/new-user-approve/faq/), it does not list 4.3 as being compatible, though the support forums don’t necessarily suggest it’s not. * When I grep the contents of all the files on the account, I discover the following: * root@tao [/home/mysite/public_html]# grep -R set_html_content_type wp-content/ plugins/new-user-approve/new-user-approve.php: add_filter( ‘wp_mail_content_type’,‘ set_html_content_type’ ); wp-content/plugins/new-user-approve/new-user-approve. php: remove_filter( ‘wp_mail_content_type’, ‘set_html_content_type’ ); wp-content/ plugins/new-user-approve/new-user-approve.php: public function set_html_content_type(){ * The error that you’ve reported is being caused by the new-user-approve plugin as it’s using some outdated function. * Thread Starter [ty5280](https://wordpress.org/support/users/ty5280/) * (@ty5280) * [10 years, 9 months ago](https://wordpress.org/support/topic/call-back-functions-header-modify-errors/#post-6526428) * So I paid a developer to fix this code. Please add and release an update. * The current version of the plugin does not fail on all server configurations ( which caused a lot of time wasted troubleshooting!). * But please fix this so others don’t waste time and money! * Issue: Function was being called before declaring it. * File Changed: new-user-approve/new-user-approve.php * Removed “public” in front of the function: * Before: * public function set_html_content_type() { return ‘text/html’; } * After: * function set_html_content_type() { return ‘text/html’; } Viewing 3 replies - 1 through 3 (of 3 total) The topic ‘Call Back Functions & Header Modify Errors’ is closed to new replies. * ![](https://ps.w.org/new-user-approve/assets/icon-128x128.gif?rev=2544141) * [New User Approve](https://wordpress.org/plugins/new-user-approve/) * [Frequently Asked Questions](https://wordpress.org/plugins/new-user-approve/#faq) * [Support Threads](https://wordpress.org/support/plugin/new-user-approve/) * [Active Topics](https://wordpress.org/support/plugin/new-user-approve/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/new-user-approve/unresolved/) * [Reviews](https://wordpress.org/support/plugin/new-user-approve/reviews/) * 3 replies * 1 participant * Last reply from: [ty5280](https://wordpress.org/support/users/ty5280/) * Last activity: [10 years, 9 months ago](https://wordpress.org/support/topic/call-back-functions-header-modify-errors/#post-6526428) * Status: resolved