Suppress bogus PHP imap_open() Notice: insecure server advertised AUTH=PLAIN - imap

Question

I'm getting a mess of these bogus warnings in my log file, and I’d like to suppress them without suppressing legitimate messages:
PHP Notice: Unknown: SECURITY PROBLEM: insecure server advertised AUTH=PLAIN (errflg=1) in Unknown on line 0
(I’m connecting to an IMAP service that is only listening to localhost on a server with no third-party users.)

Answer 1

One thing you can do is use the imap_errors and imap_alerts functions, place this code before your imap_close.
imap_errors();
imap_alerts();
What these functions do is return all errors and alerts that have occured and then flushes them. If you do not call these functions they are issued as notices when imap_close() is called, or the page dies.

Answer 2

As deceze said, it's not really a "bogus" message, it just means that it's a plaintext unencrypted connection.
Here is how you can do :
$error = imap_errors();
if (count($error) > 1 || $error[0] != 'SECURITY PROBLEM: insecure server advertised AUTH=PLAIN') {
// More than 1 error or not the expected error
var_dump($error);
throw new Exception('IMAP error detected');
}

Answer 3

You can get all warnings and errors while suppressing notices using this:
error_reporting(E_ALL & ~E_NOTICE & ~E_USER_NOTICE);
The bit-level error reporting flags are:
Error Bit Purpose
###############################################################################
E_ALL All errors and warnings (doesn't include E_STRICT)
###############################################################################
E_ERROR Fatal run-time errors
###############################################################################
E_WARNING Run-time warnings (non-fatal errors)
###############################################################################
E_PARSE Compile-time parse errors
###############################################################################
E_NOTICE Run-time notices (these are warnings which often result
from a bug in your code, but it's possible that it was
intentional (e.g., using an uninitialized variable and
relying on the fact it's automatically initialized to
an empty string)
###############################################################################
E_STRICT Run-time notices, enable to have PHP suggest changes to
your code which will ensure the best interoperability
and forward compatibility of your code.
###############################################################################
E_CORE_ERROR Fatal errors that occur during PHP's initial startup
###############################################################################
E_CORE_WARNING Warnings (non-fatal errors) that occur during PHP's
initial startup
###############################################################################
E_COMPILE_ERROR Fatal compile-time errors
###############################################################################
E_COMPILE_WARNING Compile-time warnings (non-fatal errors)
###############################################################################
E_USER_ERROR User-generated error message
###############################################################################
E_USER_WARNING User-generated warning message
###############################################################################
E_USER_NOTICE User-generated notice message
###############################################################################
You can also set ignore_repeated_errors to TRUE/1 so that it doesn't flood your log as well.
ini_set('ignore_repeated_errors',1);