Why this happens

PHP is a strict language - a missing semicolon, an unclosed bracket, or a stray character anywhere in a file will stop the entire script from running. This almost always happens right after a file was manually edited, whether by you, a developer, or a plugin's automatic update process being interrupted partway through.

Step-by-step fix

  1. The error message will show the exact file name and line number (e.g. functions.php on line 42).
  2. Open that file in File Manager and check around that line number.
  3. If you recently edited something yourself, undo or remove that change.
  4. If it's a theme's functions.php, restore a working copy from a backup.
  5. Edit the file via FTP/File Manager rather than WordPress's built-in editor until the issue is fixed.

How to prevent it happening again