On Fr, 2017-06-02 at 13:12 -0400, Michael Morris wrote:
> What about foreach by reference, which is honestly the only time I
> use referencing anymore...
>
> foreach ($array as $key => &$value) {
> $value = someOp($value);
> }
>
> Is this also bad?
If someOp() takes parameters by value this code disables copy-on-write
and during the function call $value has to be duplicated. If the
iteration would use values then copy-on-write can be effective and
avoid copying.
But for modification this indeed is a case where references might be
useful, in the simplified example.
foreach ($array as $key => &$value) {
$value++;
}
is nicer and faster than (at least in my expectation, haven't measured)
foreach ($array as $key => &$value) {
$arry[$key] = $value+1;
}
Some might argue that using array_map() would be even nicer style, while then
we have more function calls (even though internally cached lookups so they are
a bit faster than direct function calls)
For a larger and more realistic case the performance calculation becomes
complicated, but often the extra copies cost more. But then again since PHP 7
for "simple types" a copy is relatively cheaper than before. (actually they
don't have copy-on-write anymore, but references still need special treatment
...)
johannes
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