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KO Headers Sent Diagnostic

Logs the first PHP file and line that sent output before WordPress could send headers.

by KO · github.com/wy4tt34rp/ko-headers-sent-diagnostic

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Install

No release zip yet. The repository archive installs, but the folder name will carry the branch suffix and updates will not flow:

wp plugin install https://github.com/wy4tt34rp/ko-headers-sent-diagnostic/archive/refs/heads/main.zip
Readme github.com/wy4tt34rp/ko-headers-sent-diagnostic ↗

DEX early-output diagnostic

The DEX login response currently begins with two line-feed bytes before the <!DOCTYPE html> declaration. That makes PHP report that headers have already been sent, preventing WordPress from setting its login test cookie.

Install

  1. Ensure wp-content/mu-plugins/ exists on the DEX development site.
  2. Upload ko-headers-sent-diagnostic.php directly into that directory. It must be directly inside mu-plugins, not inside another folder.
  3. Request https://dex.dev.velaagency.com/wp-login.php once.
  4. Download wp-content/ko-headers-sent-diagnostic.log.

The log entry will resemble:

[KO headers diagnostic] Early output detected during plugins_loaded. Output started at /path/to/wp-content/plugins/example/example.php:123

The reported file and line identify where the first output began. Common fixes are removing bytes before <?php, removing a trailing ?> and its whitespace, saving the file as UTF-8 without BOM, or removing accidental debug output.

Remove

Delete wp-content/mu-plugins/ko-headers-sent-diagnostic.php and wp-content/ko-headers-sent-diagnostic.log after correcting the source file.