Detect (in custom error handler) if a PHP error was actually suppressed by @

Question

Context:

I have three environments for an app: dev (local), test/staging (prod server), production. The app knows which is which. Error reporting on both staging and production is 0, so errors are never shown. On dev I want to see errors immediately and I want to see them where they happen, so not in some log, but in the code's result.

However, I don't want to see the errors I have explicitly suppressed with @. I've been using fsockopen and that throws a warning when it can't connect. I accept the no-connection, but don't want to see the error. Not even on dev.

Apparantly all errors go though the custom error handler, even if they were suppressed in the code.

My error handler has only 4 arguments: errno, error, file, line. From those I can't see whether the error was originally suppressed or not. If I can see that there, I can choose whether to print the error (right now I always do, if env=dev).

Any ideas? Or maybe on how to completely ignore suppressed errors (so that they don't even reach the custom error handler)?

Answer 1

There's a hint to this in the set_error_handler manual page.

[the error_reporting()] value will be 0 if the statement that caused the error was prepended by the @ error-control operator

When you use the error control operator @, what is happening is this:

1. error reporting is set to 0 (no errors) - error_reporting(0)
2. the expression is evaluated
3. error reporting is set back to the previous value (ie turned back on)

The slightly confusing quote above refers to the fact that error_reporting returns the current setting. If you have suppressed the error with the control operator, calling error_reporting() will return 0.

Therefore, if you know you have set it to non-zero (ie you are reporting some errors) and it returns zero, you know the error was suppressed.

If you detect a suppressed error and want to know what it was, you can find it in the variable $php_errormsg (if track_errors is set to true in php.ini).

Note that the error control operator causes a lot of overhead, as it changes the error reporting level twice each time it is used. It will slow down your script.