Advanced PHP Error Handling via htaccess
In my previous article on logging PHP errors, How to Enable PHP Error Logging via htaccess, we observed three fundamental aspects of preventing, preserving, and protecting your site’s PHP errors.
Prevent public display of PHP errors via htaccess
# supress php errors php_flag display_startup_errors off php_flag display_errors off php_flag html_errors off php_value docref_root 0 php_value docref_ext 0
Preserve (log) your site’s PHP errors via htaccess
# enable PHP error logging php_flag log_errors on php_value error_log /home/path/public_html/domain/PHP_errors.log
Protect your site’s PHP error log via htaccess
# prevent access to PHP error log <Files PHP_errors.log> Order allow,deny Deny from all Satisfy All </Files>
Now, in this article, we will explore these operations1 in greater depth, provide additional functionality, and examine various implications. First we will explore PHP error handling for production environments (i.e., for websites and applications that are online, active, and public), then we will consider error handling for development environments (i.e., for projects that are under development, testing, private, etc.).
Controlling the level of PHP error reporting
Using htaccess, it is possible to set the level of error reporting to suit your particular needs. The general format for controlling the level of PHP errors is as follows:
# general directive for setting php error level php_value error_reporting integer
There are several common values used for “integer”, including:
- Complete error reporting — for complete PHP error logging, use an error-reporting integer value of “
8191”, which will enable logging of everything except run-time notices2.
- Zend error reporting — to record both fatal and non-fatal compile-time warnings generated by the Zend scripting engine, use an error-reporting integer value of “
- Basic error reporting — to record run-time notices, compile-time parse errors, as well as run-time errors and warnings, use “
8” for the error-reporting integer value.
- Minimal error reporting — to record only fatal run-time errors, use an error-reporting integer value of “
1”, which will enable logging of unrecoverable errors.
Of course, there are many more error-reporting values available, depending on your particular error-logging goals. For more information on logging PHP errors, refer to the Error Handling and Logging Functions page at php.net.
Setting the maximum file size for your error strings
Using htaccess, you may specify a maximum size for your PHP errors. This controls the size of each logged error, not the overall file size. Here is the general syntax:
# general directive for setting max error size log_errors_max_len integer
Here, “integer” represents the maximum size of each recorded error string as measured in bytes. The default value is “
1024” (i.e., 1 kilobyte). To unleash your logging powers to their fullest extent, you may use a zero value, “
0”, to indicate “no maximum” and thus remove all limits. Note that this value is also applied to displayed errors when they are enabled (e.g., during development).
Disable logging of repeated errors
If you remember the last time you examined a healthy (or sick, depending on your point of view) PHP error log, you may recall countless entries of nearly identical errors, where the only difference for each line is the timestamp of the event. If you would like to disable this redundancy, throw down the following code in the htaccess file of your project root:
# disable repeated error logging php_flag ignore_repeated_errors on php_flag ignore_repeated_source on
With these lines in place, repeated errors will not be logged, even if they are from different sources or locations. If you only want to disable repeat errors from the same source or file, simply comment out or delete the last line. Conversely, to ensure that your log file includes all repeat errors, change both of the
on values to
Putting it all together — Production Environment
Having discussed a few of the useful ways to customize our PHP error-logging experience, let’s wrap it all up with a solid, htaccess-based error-handling strategy for generalized production environments. Here is the code for your target htaccess file:
# PHP error handling for production servers php_flag display_startup_errors off php_flag display_errors off php_flag html_errors off php_flag log_errors on php_flag ignore_repeated_errors off php_flag ignore_repeated_source off php_flag report_memleaks on php_flag track_errors on php_value docref_root 0 php_value docref_ext 0 php_value error_log /home/path/public_html/domain/PHP_errors.log # [see footnote 3] # php_value error_reporting 999999999 php_value error_reporting -1 php_value log_errors_max_len 0 <Files PHP_errors.log> Order allow,deny Deny from all Satisfy All </Files>
Or, if you prefer, an explanatory version of the same code, using comments to explain each line:
# PHP error handling for production servers # disable display of startup errors php_flag display_startup_errors off # disable display of all other errors php_flag display_errors off # disable html markup of errors php_flag html_errors off # enable logging of errors php_flag log_errors on # disable ignoring of repeat errors php_flag ignore_repeated_errors off # disable ignoring of unique source errors php_flag ignore_repeated_source off # enable logging of php memory leaks php_flag report_memleaks on # preserve most recent error via php_errormsg php_flag track_errors on # disable formatting of error reference links php_value docref_root 0 # disable formatting of error reference links php_value docref_ext 0 # specify path to php error log php_value error_log /home/path/public_html/domain/PHP_errors.log # specify recording of all php errors # [see footnote 3] # php_value error_reporting 999999999 php_value error_reporting -1 # disable max error string length php_value log_errors_max_len 0 # protect error log by preventing public access <Files PHP_errors.log> Order allow,deny Deny from all Satisfy All </Files>
This PHP error-handling strategy is ideal for a generalized production environment. In a nutshell, this code secures your server by disabling public display of error messages, yet also enables complete error transparency for the administrator via private error log. Of course, you may wish to customize this code to suit your specific needs. As always, please share your thoughts, ideas, tips and tricks with our fellow readers. Now, let’s take a look at a generalized error-handling strategy for development environments..
Putting it all together — Development Environment
During project development, when public access to your project is unavailable, you may find it beneficial to catch PHP errors in real time, where moment-by-moment circumstances continue to evolve. Here is a generalized, htaccess-based PHP error-handling strategy for development environments. Place this code in your target htaccess file:
# PHP error handling for development servers php_flag display_startup_errors on php_flag display_errors on php_flag html_errors on php_flag log_errors on php_flag ignore_repeated_errors off php_flag ignore_repeated_source off php_flag report_memleaks on php_flag track_errors on php_value docref_root 0 php_value docref_ext 0 php_value error_log /home/path/public_html/domain/PHP_errors.log # [see footnote 3] # php_value error_reporting 999999999 php_value error_reporting -1 php_value log_errors_max_len 0 <Files PHP_errors.log> Order allow,deny Deny from all Satisfy All </Files>
For this code, we will forego the line-by-line explanations, as they may be extrapolated from the previous section. This PHP error-handling strategy is ideal for a generalized development environment. In a nutshell, this code enables real-time error-handling via public display of error messages, while also enabling complete error transparency for the administrator via private error log. Of course, you may wish to customize this code to suit your specific needs. As always, please share your thoughts, ideas, tips and tricks with our fellow readers. That’s all for this article — see you next time!
- 1 For more information, check out the manual on Error Handling and Logging Functions at php.net
- 2 Due to the bitwise nature of the various error-reporting values, the value for logging all errors continues to increase. For example, in PHP 5.2.x, its value is
6143, and before that, its value was
2047. Thus, to ensure comprehensive error logging well into the future, it is advisable to set a very large value for
error_reporting, such as
- 3 According to the PHP Manual on error_reporting, “Passing in the value
-1will show every possible error, even when new levels and constants are added in future PHP versions. The
E_ALLconstant also behaves this way as of PHP 6.” – Thus, the code in this article has been updated accordingly. Simply delete the commented-out line in the code and you’re good to go.
That’s quite a good idea; too bad it’s not working on my shared hosting :/
As discussed elsewhere, it seems that PHP error logging has, for whatever reason, been disabled on your shared hosting account. I assure you, these are standard methods that will work (I use them myself) on any capable server.
Thanks for tips … it worked on my (only ftp access) server.
Sure thing, styx — thanks for the feedback! ;)
Just wanted to say thanks for such a succinct and informative article. This is *exactly* what I needed to know. Very much appreciated.
My pleasure! I am very glad this article has proven helpful for you. Thank you for the positive feedback! :)
Very nice job to put all the information together with adequate explanations. Thanks indeed !
Happy to help, Christelle — thanks for the feedback! :)
A bit earlier I came accross of a very basic error handling instruction.
But your articles gives so much more – an excelent in-depth tutorial for a newbie. And surprisingly it is easy to understand and it does work!! [5 stars!]
Thank you, Perishable
Thank you for the positive feedback, mmdesign! It is much appreciated! :)
Great article, and much-needed information, especially for new developers.
A couple of points of note, however.
1.) You should not use the
# specify recording of all php errors
php_value error_reporting 999999999
because that causes the error output that should ONLY be logged to be sent to the browser on many POSIX systems! Visitors to the site will see every single error PHP is logging, right in the browser window on every page!
Instead, you should use
E_ALL, or a combination of the predefined constants. Using ANY integer value in this case is a bad idea, since they are subject to change. That is precisely why the constants exist!
2.) There is a small syntax error in your sample file (you forgot the
php_valueat the very bottom):
# disable max error string length
should instead be
# disable max error string length
php_value log_errors_max_len 0
Hi Ben, thank you for sharing this information. I had no idea that POSIX systems behaved this way. Question: is it safe to use
error_reportinggiven large enough reporting values on non-POSIX systems? I am trying to keep this article as general as possible, without requiring too much fiddling with various predefined-constant configurations. Perhaps simply replacing
E_ALLwould do the trick? In either case, I am going to revise the article to reflect this information and will post a followup comment here as well to signal the update.
Also, thanks for the catch on the missing
php_value. There were
twothree instances of this omission and bothall have now been corrected. Thank you! :)