Updated on 20/01/2016 for OpenCart 2.x
Even though it's 2016, you may still encounter the dreaded Blank Screen of Death or an Internal Server Error when moving your OpenCart store, installing new extensions or just performing a regular update. We've revised and updated this post to account for new version of OpenCart.
This post covers blank pages and internal server errors. If you're struggling with JSON.parse errors in OpenCart, see our other blog post.
First things first – find the actual cause
It is important to understand, that blank pages and internal server errors don't have a single common cause – it simply means something went wrong with your store somewhere, therefore it couldn't load. To find out the actual reason for this, you need to look into your server's error log and find the exact error message.
Since the location of the main server error log varies between hosting providers, you'll need to look up the documentation for your particular hosting provider. In most cases, however, you can also display the contents of the log through your server's administration software (e.g. CPanel).
If you've found the log, but it's empty, you'll need to make sure your errors are getting logged. To do this, make sure your log is writable and verify the values of the following PHP variables in your php.ini file: display_errors and log_errors. They are usually set to Off and On in production respectively, but you can change both of them to On for debugging purposes.
If none of this seems to work you can add the following lines of code to the beginning of your index.php file for this debugging session:
Now when you have the error message, it's time to fix this!
Here are the most common issues for blank pages in OpenCart.
Broken configuration files
This is a common problem that can happen after you move your store to a different server.
OpenCart stores various pieces of its main configuration in two files: config.php and admin/config.php. If you're moving your store to a different domain or a different server, you may need to adjust some or all of them.
Double check your main store URL in HTTP_ and HTTPS_ variables, paths to your OpenCart setup in DIR_ variables and the database configuration in DB_ variables. All of them should match your new server setup.
Broken directory structure
Although this is a less common cause of blank pages in OpenCart, it is still worth mentioning. Both admin and catalog folders must follow the same structure in OpenCart:
/catalog/ or /admin/
You may get a blank page with no errors if this structure is missing the controller/ folder. Just make sure the folders are in place.
Even though it's 2016 out there, we still see servers with magic quotes enabled once in a while. This can cause all kinds of issues, including problems resulting in blank pages. Make sure to disable them once and for all.
Syntax errors of all kinds
Syntax errors can happen to anyone – an extra bracket, a forgotten comma or a broken extension or vQmod file can easily turn your beautiful store into a blank page. Fortunately, they're usually easy to fix.
This is what a common syntax error may look like:
[Thu Jan 21 12:48:37 2012] [error] [client 127.0.0.1] PHP Parse error: syntax error, unexpected '}' in /srv/www/dev/opencart/2101/index.php on line 47
Now all you need to do is open up that file and fix that error! Easy.
However, make sure the file name is now one of vQmod's cache files – they usually look somewhat like this: vqmod/vqcache/vq2-catalog_controller_checkout_cart.php. In this case, editing the file directly won't work as it will be overwritten by vQmod.
To fix this, you'll need to find the particular vQmod modification that's causing problems and disable it until you find a way to fix the error. We suggest searching for the particular piece of code from the error message inside your vqmod/xml/ folder (using Notepad++ file search, for example) and then disabling the broken vQmod file by changing it's extension to .xml_. This will bring your store back to life while you're writing an angry message to the developer of this particular modification.
Notice: Error: E-Mail to required!
This particular error can be caused by two things – a bug in OpenCart 220.127.116.11 or email missing from your store's configuration. If you're still using OpenCart 18.104.22.168, you should definitely update to the latest version available, otherwise make sure your email settings are correct in Admin > Settings > Your Store > System > Email.
Error: Table doesn't exist
Error: Unknown column in 'field list'
These errors mean OpenCart is trying to access a database table or a field that is missing. This is almost exclusively caused by third party modules and themes – and since the cause of this lies within the extension itself, the best way to fix it is to reinstall the theme or extension and contact the developers if this doesn't help.
Warning: fsockopen(): unable to connect to http://yourdomain.com:25/
This error indicates a problem with either your mail configuration in OpenCart or with your mailserver. Make sure that your mail settings are correct in Admin > Settings > Your Store > System > Email and that your mailserver is up and running.
These are the most common causes and solutions for blank pages and internal server errors in OpenCart. Hopefully by now you've fixed your issue, but if not – feel free to comment down below and we'll see if we can help.