Cannot modify header information – headers already sent

  • Resolved Insect Trojan

    (@insecttrojan)


    11 months, 4 weeks ago

    hello i have error on the

    [21-Apr-2025 09:23:41 UTC] PHP Warning: Cannot modify header information – headers already sent in /home/in584323/public_html/wp-content/plugins/wordfence/vendor/wordfence/wf-waf/src/lib/utils.php on line 759
    [21-Apr-2025 09:23:41 UTC] PHP Warning: Cannot modify header information – headers already sent in /home/in584323/public_html/wp-content/plugins/wordfence/vendor/wordfence/wf-waf/src/lib/utils.php on line 760
    [21-Apr-2025 09:23:41 UTC] PHP Warning: Cannot modify header information – headers already sent in /home/in584323/public_html/wp-content/plugins/wordfence/vendor/wordfence/wf-waf/src/lib/utils.php on line 761
    [21-Apr-2025 09:23:41 UTC] PHP Warning: Cannot modify header information – headers already sent in /home/in584323/public_html/wp-content/plugins/wordfence/vendor/wordfence/wf-waf/src/lib/waf.php on line 1181

    the lines is them 

    public static function doNotCache() {
    header("Pragma: no-cache");
    header("Cache-Control: no-cache, must-revalidate, private, max-age=0");
    header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); //In the past
    if (!defined('DONOTCACHEPAGE')) { define('DONOTCACHEPAGE', true); }
    if (!defined('DONOTCACHEDB')) { define('DONOTCACHEDB', true); }
    if (!defined('DONOTCDN')) { define('DONOTCDN', true); }
    if (!defined('DONOTCACHEOBJECT')) { define('DONOTCACHEOBJECT', true); }
}

    The page I need help with: [log in to see the link]

Viewing 1 replies (of 1 total)
  • Plugin Support wfmargaret

    (@wfmargaret)

    11 months, 4 weeks ago

    Hi @insecttrojan,

    The “Cannot modify header information – headers already sent by” error message typically indicates that something in your PHP code has caused output to be sent before the HTTP headers are fully defined. It’s been linked to another plugin loading WordPress core files out of order in the past, which is a possibility here.

    To rule out a plugin or theme conflict, try to run Wordfence as your only enabled plugin and revert to a default theme such as Twenty Twenty-Five. If you no longer see the error, re-enable your plugins and theme one-by-one until it recurs again to help find the cause.

    Thanks,
    Margaret

Viewing 1 replies (of 1 total)

The topic ‘Cannot modify header information – headers already sent’ is closed to new replies.