I ran into a gotcha today coding a PHP script... The funny thing about
it is that I've been writing PHP for years and haven't run into this one
before.. The pattern is
function process_info() {
foreach ($this->get_items() as $item) {
// $data=array() <--- this should have been here,
but wasn't
$data["X"]=$item->Y;
if ($item->bar) {
$data["foo"]=$item->bar;
}
$this->do_something_with_transformed_data_array($data);
}
}
I was mystified by the behavior of the script -- eventually it dawned on
me that I wasn't initializing the $data array with each loop... I
wanted $data["foo"] to be undefined if $item->bar evaluates false,
however, the value of "foo" was persisting between iterations, causing
do_something_with_transformed_data_array to behave horribly wrong...
In some languages (C#, for instance), variables declared at a
point in a loop come into existence at that point in the loop, and
don't have any life from one iteration to the next -- that kind of
scoping certainly makes this kind of error less likely (unless $data was
defined in front of the loop.)
What I find interesting is that I don't remember ever making this
sort of mistake in the past...
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