Warning: Cannot modify header information error when saving settings

Looks an echo in class.options.php on line 40 is causing this issue. It should be used as an notification to notify the user that the settings have been saved.

Because of this echo, content is being sent to the client and therefor the headers can no longer be sent.

Hi,
I’am not sure why this issue might occur for you, as the admin dashboard use output buffering anyway, so the headers can be pushed. Also there should be other html data in place, before this message output, so it shouldn’t make any difference.

Possible the warning is showing up in conjunction with another plugin? Also which php version you use?

Thanks

I realize this topic is 7 months old but I’m having the same issue. I’ve disabled all plugins and have tried both PHP 5.6.21 and 7.0.6 and am still having the same result.

Here are the errors I’m receiving:

Warning: Cannot modify header information - headers already sent by (output started at /domain-path/html/wp-content/plugins/post-types-order/include/class.options.php:40) in /domain-path/html/wp-admin/includes/misc.php on line 1126

Warning: Cannot modify header information - headers already sent by (output started at domain-path/html/wp-content/plugins/post-types-order/include/class.options.php:40) in /domain-path/html/wp-includes/option.php on line 919

Warning: Cannot modify header information - headers already sent by (output started at /domain-path/html/wp-content/plugins/post-types-order/include/class.options.php:40) in /domain-path/html/wp-includes/option.php on line 920

@thepeel can you ask for more help at https://www.nsp-code.com ?

I get exactly the same error at line 40 when saving settings.

I just got a fix for this.

By replacing

echo '<div class="updated fade"><p>' . esc_html__('Settings Saved', 'post-types-order') . '</p></div>'; (line #40)

with the following

add_action('admin_head', function(){
   echo '<div class="updated fade"><p>' . esc_html__('Settings Saved', 'post-types-order') . '</p></div>';
}, PHP_INT_MAX);

PHP_INT_MAX will make sure that printing message gets the lowest priority.

@tdgu it would be great if you please review it once.

Thank you!