Fatal error: Cannot redeclare is_comments_popup()

Hello qdungeng,

I would guess that a plugin update has caused this. If you have FTP or a GUI file manager access, I’d suggest renaming the wp-content/plugins out of the way. This will disable all your plugins. If you can now access your site then you’ll need to rename back each plugin in turn to work out what caused the problem.

If you still get the same error then it may be a theme issue – I’d recommend going into wp-content/themes and renaming just the them you’re using to cause that to deactivate – another should activate in its place as a temporary measure.

If you still get the same error then go to this location wp-includes/query.php file

/**
* Set if query is within comments popup window.
*
* @since 1.5.0
* @access public
* @var bool
*/

public $is_comments_popup = false;

After this:
public $is_embed = false;

But its not a good idea to change in core file.
So,please update your wordpress version by create backup of your old wordpress.