White screen of death!

问题:

After debugging a codeigniter app that were installed into a new development environment, I have started to freak out when seeing white screens with nothing more available. I have been able to solve each and every one of the errors that have caused this, but it have taken seriously way too long time.

PHP error_reporting(E_ALL) & display_errors", 1 is set as well. I even installed Xdebug in hope of getting more output, but no. My logging settings are also working, but nothing is written to the log.

Is there a way to get something informative printed out instead of a complete white screen? It would certainly shorten my time spent on solving the eventual errors that causes this?

Thanks a lot!

Reference: Why does Code Igniter give me a white page?

回答1:

If there's a fatal compilation error, then you may well get a blank page. Try doing a

php -l <filename.php>

against your script

回答2:

Look near the top of /index.php for a call to error_reporting() - and make sure it's not changing your php.ini configuration to something else (besides E_ALL).

And since you didn't mention your php.ini configuration, check to ensure you have error_reporting = E_ALL there as well.

回答3:

I've found out, since the time of my question, that nothing seems to ensure that errors are always outputted with PHP, which seems to throw white screens here and there. Regardless of PHP's ini-settings.

I've found out that the best workaround however is to use the following line to ensure that error logging is put into a file easily accessed and monitoredby the application:

ini_set('error_log', MYPATH .'logs/errorlog.log'); 

As far as I've tested it, when white screens appear - it also gets logged into this errorlog. Seems to be the easiest way to know what happens when things go wrong.

回答4:

Grep the files for 'error_reporting', and 'display_errors', the application might turn it off somewhere.

Also, to be able to see parse errors, you need to set error_reporting/display_errors in the php.ini file, or a .htaccess file, setting it in the script files will not do, and will lead to the white page you describe if there are parsing errors.

回答5:

The best thing is to have a checklist of the common problems that could cause this since CI's default is already

error_reporting(E_ALL);

1. Same name controllers and models
2. using reserved words as methods

list goes on..

回答6:

Aside from everything else posted, also make sure that something masked with the @ (error suppression operator) isn't throwing a fatal error.

回答7:

Consider setting PHP's error_log configuration variable -- it can be helpful when you have code setting error_reporting() without your knowledge. Then you can check the error log and see what errors, if any, occurred.

回答8:

Make sure your logs and cache folder inside /system are chmod'ed to 777.

回答9:

I had this problem on my freshly installed server. Debian 7. I enabled logging, error reporting, disabled gzip and so on.

However, my PHP-installation did not have MySQL enabled. Enabling MySQL did the trick for me.

回答10:

Ensure that there's no whitespace in your files output outside of the CI buffer, especially if compression is turned on. You can test this by turning off compression in your CI config file.

See step two at: http://codeigniter.com/user_guide/installation/upgrade_141.html (Note that while this is for the upgrade, it contains a snippet of the config file which explains the problem.)

回答11:

Have you by chance happen to create a cached output for that particular method inside your controller. Because if so, then it may create a cached version of the page and practically that page is not even running. The cached error output page is showing up. Please check your cache folder inside the application. It should only contain the index.html file.