Why is this true?

[eluser]Steven Ross[/eluser]
I traced a bug back to sth essentially like this:

Code:

$key = 0;
if ($key == "text") {
    echo "true";
} else {
    echo "false";
}

This evaluates to TRUE. I realize it may have to do with mixing types, but IMO it should still be FALSE. PHP thinks otherwise. Why?