How to correct Apache's 'Failed to read FastCGI header' error
The error message "Failed to read FastCGI header" means that when Apache communicates with the PHP process of your hosting, the PHP process does not respond correctly. This error does not mean there is a problem with Apache itself, but that there may be several reasons why this error appears.
This error can have many variations, but most commonly, the page/plugin that generates this error will display a 503 Service Unavailable error on screen.
If you access your hosting error logs via FTP or from your cdmon control panel (Where to view hosting error logs), you will have access to your hosting error records.
There you will see the log entry generated, which should be similar to the following:
[Thu Mar 10 00:01:30.433775 2022] [proxy_fcgi:error] [pid 10000:tid 100000373888] [client 91.11.1.121:60803] AH01067: Failed to read FastCGI header, referer: https://yourdomain.com/wp-admin/users.phpAs mentioned, the reason why "Failed to read FastCGI header" appears is because Apache on your hosting cannot communicate with the server’s PHP process.
The 3 most common causes of this error are:
- An error in the application's PHP code, such as a WordPress plugin with errors
The most common cause of these errors is faulty PHP code within the application files.
The best solution is to disable all WordPress plugins, custom themes, and any other custom code until you identify which code is causing the problem.
For example, if you have scripts, a cascade of errors caused by those scripts may eventually result in PHP no longer being able to respond to requests. In this case, the solution is to fix the slow or faulty PHP code.
- Your hosting does not have enough memory
If your hosting runs out of memory while executing a PHP request and the PHP process was using a large amount of memory, the PHP process handling the request will fail.
This is not necessarily due to the server itself. cdmon hostings use PHP-FPM, so you can expand and edit your hosting’s PHP values according to your needs. Each hosting plan has a maximum memory limit.
The best solution in this case would be to upgrade your hosting plan to one with more memory or reduce the number of requests so that less memory is required.
- PHP server/hosting error
If none of the above causes match your situation, there may be a PHP incompatibility. It is possible that the PHP version assigned to your hosting is too old for the plugins and themes you have installed, or vice versa.
You can contact our technical team so they can review the PHP status of your server.
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