How can I get PHP to produce a backtrace upon errors?

Question

Trying to debug PHP using its default current-line-only error messages is horrible. How can I get PHP to produce a backtrace (stack trace) when errors are produced?

Answer 1

If you can't install a debugger then use this function sorrounding the fatal error to get the "fatal stack". Check the code and example below that explains better how to use it:

// Give an extra parameter to the filename
// to save multiple log files
function _fatalog_($extra = false)
{
    static $last_extra;

    // CHANGE THIS TO: A writeable filepath in your system...
    $filepath = '/var/www/html/sites/default/files/fatal-'.($extra === false ? $last_extra : $extra).'.log';

    if ($extra===false) {
        unlink($filepath);
    } else {
        // we write a log file with the debug info
        file_put_contents($filepath, json_encode(debug_backtrace()));
        // saving last extra parameter for future unlink... if possible...
        $last_extra = $extra;
    }
}

Here's an example of how to use it:

// A function which will produce a fatal error
function fatal_example()
{
    _fatalog_(time()); // writing the log
    $some_fatal_code = array()/3; // fatality!
    _fatalog_(); // if we get here then delete last file log
}

Finally to read the contents of the log...

var_dump(json_decode(file_get_contents('/path/to-the-fatal.log')));

Hope that helps!