Can I try/catch a warning?

Set and restore error handler

One possibility is to set your own error handler before the call and restore the previous error handler later with restore_error_handler().

set_error_handler(function() { /* ignore errors */ });dns_get_record();restore_error_handler();

You could build on this idea and write a re-usable error handler that logs the errors for you.

set_error_handler([$logger, 'onSilencedError']);dns_get_record();restore_error_handler();

Turning errors into exceptions

You can use set_error_handler() and the ErrorException class to turn all php errors into exceptions.

set_error_handler(function($errno, $errstr, $errfile, $errline) {    // error was suppressed with the @-operator    if (0 === error_reporting()) {        return false;    }        throw new ErrorException($errstr, 0, $errno, $errfile, $errline);});try {    dns_get_record();} catch (ErrorException $e) {    // ...}

The important thing to note when using your own error handler is that it will bypass the error_reporting setting and pass all errors (notices, warnings, etc.) to your error handler. You can set a second argument on set_error_handler() to define which error types you want to receive, or access the current setting using ... = error_reporting() inside the error handler.

Suppressing the warning

Another possibility is to suppress the call with the @ operator and check the return value of dns_get_record() afterwards. But I'd advise against this as errors/warnings are triggered to be handled, not to be suppressed.

The solution that really works turned out to be setting simple error handler with E_WARNING parameter, like so:

set_error_handler("warning_handler", E_WARNING);dns_get_record(...)restore_error_handler();function warning_handler($errno, $errstr) { // do something}

Be careful with the @ operator - while it suppresses warnings it also suppresses fatal errors. I spent a lot of time debugging a problem in a system where someone had written @mysql_query( '...' ) and the problem was that mysql support was not loaded into PHP and it threw a silent fatal error. It will be safe for those things that are part of the PHP core but please use it with care.

bob@mypc:~$ php -aInteractive shellphp > echo @something(); // this will just silently die...

No further output - good luck debugging this!

bob@mypc:~$ php -aInteractive shellphp > echo something(); // lets try it again but don't suppress the errorPHP Fatal error:  Call to undefined function something() in php shell code on line 1PHP Stack trace:PHP   1. {main}() php shell code:0bob@mypc:~$ 

This time we can see why it failed.