PHP try-catch blocks: are they able to catch invalid arg types?

Question

Background: Suppose I have the following obviously-incorrect PHP:

    try{
        $vtest = '';
        print(array_pop($vtest));
    }catch(Exception $exx){}

For it to work with array_pop, $vtest should obviously be an array, not a string. Nevertheless, when I run this code the Warning is exhibited. I don't want that, I just want the code to fail silently.

Question: Is there something special about PHP try-catch compared to other languages that cause this not to work?

Disclaimer: There is the standard "at-sign" trick in PHP, but I am curious about whether I can use the more language-agnostic try-catch approach as an alternative.

        $vtest = '';
        print(@array_pop($vtest)); // <-- would like to avoid this

Answer 1

The only way I can think of would be to do the following:

try{
    $vtest = '';
    if(is_array($vtest)){
        print(array_pop($vtest));
    }
    else{
        throw new NotArrayException()
    }
}catch(NotArrayException $exx){}

Of course if you just want to do this silently you could just do the following since you don't need to catch any exception:

    $vtest = '';
    if(is_array($vtest)){
        print(array_pop($vtest));
    }

Answer 2

Warnings and notices are not technically exceptions in PHP. To catch an exception it has to be explicitly thrown, and many of the built-in libraries of functions do not throw exceptions (mostly because they were written before PHP supported exceptions).

PHP is notorious for this kind of feature-bloat, where a new feature is added to the language just to say "yes, we have exception handling," even though the feature doesn't penetrate to most of the existing APIs. It would have been nice if somehow exceptions were built on top of the existing notice/warning/error framework but perhaps that is asking too much.

Answer 3

You can catch such errors when you convert every error to an exception. I have set up a little error-handling environment. Just test it - it will work.

Answer 4

A warning will always be produced by the code you provided but you can use set_error_handler to dictate how the warning is handled; i.e. you can cause it to throw an exception. Furthermore, you can use restore_error_handler to return to default error handling when your done.

function errorHandler($errno, $errstr, $errfile, $errline) {
    throw new Exception($errstr, $errno);
}
set_error_handler('errorHandler');