Wordpress random 500 internal server error

Question

Randomly i keep getting 500 internal server error and I've checked server log the only errors displayed are:

End of script output before headers: admin-ajax.php
 End of script output before headers: index.php

I've increased php memory limit and wordpress memory limit to 256m. I'm running a woocommerce shop. When i refresh a resource heavy page multiple times this is most likely when the error appears. The error also randomly goes away after about 5 minutes. I can still access the wordpress readme.html. I've renamed the plugin folder and still the error remains.

Any idea what would be causing this?

Hi there. I have previously had a very similar issue. If any content (even whitespace) accidentally appears after a php file's closing tag it can be sent to the browser. This can cause this Issue. Check the files for any content after the ?> — Matt

pennywise pennywise · Accepted Answer · 2015-07-03T14:05:54

I wanted to add this as comment, but unfortunately I don't have enough points.

This can be because of some plugin messing with HTTP headers - have you installed some plugin/theme soon before the errors start showing?

Can you enable WP_DEBUG, to see if you can catch something there, as sometimes it is more useful than the server logs.

To do this, open

wp-config.php

located in the directory where WordPress is installed and then locate the line with the code

define('WP_DEBUG', false);

and change it to

define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);

That will save the log in a file called debug.log and located in your wp-content directory. It is important step to set it log to a file, if you don't want to have errors thrown on the site.

You can also refer to this codex page.

Wordpress random 500 internal server error

3 Answers