Question

aka, Seeking generic Error Handler (ΟΚ to use commercially)

I doubt that I am the best PHP programmer around, so, although I have my own generic error handler for set_error_handler(), I wondered what others do and if there is a “best” (sorry if that sounds subjective – I just want to draw out general approaches (but even the ‘best practices’ tag has been removed from SO)).

To be objective about it, here’s what I think is needed. Please correct me if I am wrong & point me to some good code if you agree.

• I want to capture as much information as possible – without knowing what the error was.

• so, for instance, it makes sense to dump the call stack.

• and $_GET, $_POST and $_SESSION.

• and I want the call stack & Globals to be pretty-printed

• I want some ‘plain-text’ layout, not CSS & fancy JS to expand/collapse the information. My users may have to cut/paste into email or even print out & fax.

• I would like to be able to add a header of my own devising, preferably as a parameter, but I can hack the code if need be. The header might include the program version, timestamp, etc (and, in my case, I have an audit track, so I can include the user’s last few actions, which led to the crash).

• some users may allow my code to auto-email the report, some may wish to preview it forst & them email it and some may not want me to send email.

Answer 1

I suggest to go the “Exceptions” way.

Throw exceptions when there’s a user error, and you can convert php errors into exceptions, like this:

function exception_error_handler($errno, $errstr, $errfile, $errline ) {
    throw new ErrorException($errstr, 0, $errno, $errfile, $errline);
}
set_error_handler("exception_error_handler");

Albeit that this kind of behaviour works best in an OOP kind of environment. If you don’t have a single point of entry (like a frontcontroller), you may also catch loose exceptions with this:

function myException($exception)
{
    echo "<b>Exception:</b> " , $exception->getMessage();
}

set_exception_handler('myException');

Simple debugging with exceptions would go something a bit like this:

function parseException($e) {
    $result = 'Exception: "';
    $result .= $e->getMessage();
    $trace = $e->getTrace();
    foreach (range(0, 10) as $i) {
        $result .= '" @ ';
        if (!isset($trace[$i])) {
            break;
        }
        if (isset($trace[$i]['class'])) {
            $result .= $trace[$i]['class'];
            $result .= '->';
        }
        $result .= $trace[$i]['function'];
        $result .= '(); ';
        $result .= $e->getFile() . ':' . $e->getLine() . "\n\n";
    }

    return $result;
}

From there evaluating globals etc. is a walk in the park. You might look for inspiration to the Symfony Framework Debug Toolbar, which offers many of these requests.