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Comment by snorkel | Hacker News Reader

My complaint about arrays in PHP is warnings for reading a array member that may not exist, such as when reading a form input that might not be there.

    $foo = $_POST["foo"];

Undefined array key! Oh, no! Tragedy! A crime has been committed! Are you kidding? Just set $foo to undefined and let me deal with the consequences, please?

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They're notices, not warnings. They can be disabled via a simple call to the error_reporting function.

I fundamentally disagree with you though. For me, notices are very useful for identifying typos and other coding mistakes that can lead to incorrect behavior.

Consider the following lines of code:

    $user_info = array(
            'id'            => 1,
            'username'      => 'nbpoole',
            'is_guess'      => false
    );

    if (!$user_info['is_guest'])
    {
            echo 'Member stuff';
    }

When I run that script with error_reporting set to E_ALL, I get an "undefined index" notice pointing me to the line where I do the comparison: at that point, I can track down where in my code I misspelled the word guest. Without the notice, I might not immediately realize that the 'is_guest' index was mis-spelled somewhere.

You really wouldn't like Python or even stricter languages such as Scala or java, then. In Python, an attempt to access a nonexistent dictionary key will throw an exception which halts execution if not caught. (similar to calling a nonexistent method or function in PHP, but since PHP doesn't have a well-thought out exception system/std. lib as Python does, you can't catch anything in that situation in PHP).

In Python, if you're expecting a potentially missing key, you can just use dict.get('key') rather than dict['key']. The equivalent in PHP would be something like:

  $val = array_key_exists('key', $dict) ? $dict['key'] : NULL;

Being able to say "I expect a potentially nil value (and am okay with that)" via get() rather than array index is both semantically useful, and far more beautiful than the PHP equivalent.

Sure, or you can catch a KeyError and do something else entirely. I'm aware of all this, just pointing out some differences to the person to whom I replied.

Python's dict.get is a bit like the getOrElse found in Scala. It's quite handy and can be seen as advanced conceptually.

I actually added some code like that to a recent post about PHP here: http://news.ycombinator.com/item?id=2771304

The more so because get() can also take a default value to return if the key is not present in the dict ;-)

I think those warnings are very helpful. They help to develop better and more secure code.

Ever tried to assign a non-existing variable in another language? I think you will get a compile error.

This isn't too hard:

  $foo = isset($_POST["foo"]) ? $_POST["foo"] : null;

This is exactly what PHP does. Yes, it issues you a notice, not a warning, not an exception. And it does not break execution. Just set your error_reporting variable to a lower level, and you won't get the Notice at all.

I think they're helpful too! Just use isset() to check whether variables exist, and you shouldn't get any errors unless you make a mistake (in which case, wouldn't it be nice to know?).

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