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Request #22839 Error messages go to STDOUT instead of STDERR
Submitted: 2003-03-24 02:14 UTC Modified: 2007-07-24 14:23 UTC
From: gk at proliberty dot com Assigned: jani (profile)
Status: Closed Package: Feature/Change Request
PHP Version: 5CVS, 4CVS (2007-07-13) OS: *
Private report: No CVE-ID: None
View Developer Edit
 [2003-03-24 02:14 UTC] gk at proliberty dot com 
Error messages should go to /dev/stderr instead of /dev/stdout

Example: redirect STDOUT to /dev/null; notice error message does not appear below:
[root@p3 php4-STABLE-200303210630]# sapi/cli/php -r "f();" 1>/dev/null
[root@p3 php4-STABLE-200303210630]# 

This is what you should see on /dev/stderr:
[root@p3 php4-STABLE-200303210630]# sapi/cli/php -r "f();"

Fatal error: Call to undefined function:  f() in Command line code on line 1


The problem is due to the default error handler; if you install a custom error handler function with set_error_handler() then you can work around the problem for errors except the following which CANNOT be handled with set_error_handler() function: 
E_ERROR, E_PARSE, E_CORE_ERROR, E_CORE_WARNING, E_COMPILE_ERROR and E_COMPILE_WARNING.

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 [2003-03-24 06:33 UTC] sniper@php.net 
Works fine when you have set it correctly in php.ini:

# php -d log_errors=1 -d error_log=/dev/stderr -r "f();" 1>/dev/null
 [2007-06-29 20:13 UTC] gk at proliberty dot com 
This is not about where  errors be LOGGED, but about what output stream to write DISPLAY output to.
I am arguing that if display_errors is enabled, then this output should go to /dev/stderr, not to /dev/stdout. 

sniper@php.net describes a workaround that co-opts use of error_log file from its intended purpose (logging errors to a file, for archival purposes) in order to redirect display output.

Most well-behaved programs distinguish between 'normal' display output and 'errors' and use /dev/stdout and /dev/sterr appropriately, in this regard.
PHP breaks this convention by displaying errors on /dev/stdout instead of /dev/stderr UNLESS you employ the workaround of setting /dev/stderr as the logfile.

If sniper's workaround is employed, however, then this prevents logging errors to a file. 

The behavior of PHP appears confused.

PHP should offer two clearly separated output mechanisms to the programmer:
1. echo() - for sending 'normal' output to /dev/stdout
2. trigger_error() - for sending 'errors' to /dev/stderr

In my case, I am running php scripts via cron. I always want to maintain a historical record, via error_log, but I also need cron to email any true errors immediately - I don't want to set error_log = /dev/stderr and lose the historical error_log record in order to accomplish this simple task that would be a no-brainer if my script was written in bash instead of php.
 [2007-07-18 15:29 UTC] jani@php.net 
I have created a patch to improve this situation a bit:

http://pecl.php.net/~jani/patches/errors_to_stderr.patch

Might need some tuning but this should work.
I overloaded the display_errors php.ini directive,
it allows using 'stderr' as parameter which makes all error messages output in CLI/CGI to go to STDERR.

Works fine in *nix, I haven't tested in Windows..
 [2007-07-24 14:23 UTC] jani@php.net 
The patch is applied to HEAD (PHP 6) and PHP_5_2 branches. 
By setting 'display_errors = "stderr"' in php.ini the error messages are outputted to STDERR. It won't affect other SAPIs than CGI/CLI, for others it's same as "On".

Note: This feature won't be added to PHP 4.
 
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