Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

Hint: Try changing the error to E_USER_WARNING instead.
(fatal errors stop script processing and are..eh..FATAL..:)

At least if ob_start is called like e.g.

ob_start(NULL, 0, PHP_OUTPUT_HANDLER_CLEANABLE | PHP_OUTPUT_HANDLER_REMOVABLE);

it should (as far as I understand) forbid to flush the buffer contents even on error.

Output buffer is flushed when PHP terminates execution. Current PHP cannot catch E_ERROR. This prevents cleaning up buffer, but not E_USER_ERROR. e.g.

set_error_handler(function ($errno, $errstr, $errfile, $errline)
{
    if (!(error_reporting() & $errno)) {
        // This error code is not included in error_reporting
        return;
    }

    switch ($errno) {
    case E_USER_ERROR:
        ob_clean(); //////////////// CLEAN UP BUFFER //////////////////////
        echo "<b>My ERROR</b> [$errno] $errstr<br />\n";
        echo "  Fatal error on line $errline in file $errfile";
        echo ", PHP " . PHP_VERSION . " (" . PHP_OS . ")<br />\n";
        echo "Aborting...<br />\n";
        exit(1);
        break;

    case E_USER_WARNING:
        echo "<b>My WARNING</b> [$errno] $errstr<br />\n";
        break;

    case E_USER_NOTICE:
        echo "<b>My NOTICE</b> [$errno] $errstr<br />\n";
        break;

    default:
        echo "Unknown error type: [$errno] $errstr<br />\n";
        break;
    }

    /* Don't execute PHP internal error handler */
    return true;
});


ob_start();
echo 'test';
trigger_error('error', E_USER_ERROR);
$output = ob_get_contents();
ob_end_clean();
?>

We have not many problematic E_ERRORs in our code base now. Most problematic E_ERRORs are in SOAP module.

One possible way to create a fatal error (ok, only if programmer is lazy)

function foo() ...


if (<usually false>)
    foop();  // spelling error


As long as the if-clause is false the error won't be noticed.

Instead of requesting changes in output buffer, request use of exception or make E_ERROR catchable.