Description:
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I recently had a bug in my code that overwrote an array with a string. I missed the [], it happens.
But debugging was hard, and I had a bunch of $array["foo"] = "bar"; when $array had been overwritten by a string.
As kind people on #php explained to me, PHP treats any string as 0. While I can understand such behaviour, I think there should be a warning like "you are treating a string as an array" or something.

This warning should probably not occur when the key is a number, as this would return the character, but when accessing a string key of a string makes no sense.

I can't see how this would break any backward compatibility, and it would make debugging much easier! 

Edit: I've now seen that there are similar bugs, all marked closed and without any non-stock explanation. 
I would really like to know why this "is expected", because to me, having developed in PHP for two years, this wasn't expected at all, and caused me a good headache.
Pardon me if I am spamming, I would prefer to add a comment to those bugs, but can't.

Reproduce code:
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$array = array();
$array = "string";
$array["foo"] = "bar";

Expected result:
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Would be nice if it produced a warning on line 3, "Trying to access a string as an array"