Re: Small question about performance

On Thu, Mar 15, 2012 at 5:39 PM, Paul Dragoonis <dragoonis@gmail.com> wrote: > On Thu, Mar 15, 2012 at 4:54 PM, Nikita Popov <nikita.ppv@googlemail.com> wrote: >> On Thu, Mar 15, 2012 at 5:22 PM, Patrick ALLAERT <patrickallaert@php.net> wrote: >>> 2012/3/15 Nikita Popov <nikita.ppv@googlemail.com>: >>>> If I am understanding the text correctly it is saying that >>>>    $f1 = f1(); >>>>    $f2 = f2($f1); >>>>    $f3 = f3($f2); >>>> is using more memory than >>>>    $f3 = f3(f2(f1())); >>>> >>>> For me this doesn't make any sense. In the latter case PHP will also >>>> create temporary variables to store the return values. There should be >>>> no difference in memory consumption. >>> >>> It does make sense to me. >>> >>> In the first case, when calling f3(), $f1 is still referenced. >>> In the second case, when calling f3(), the result of f2() is >>> referenced, but there is no more active reference to the result of >>> f1(). >> I don't really know when PHP frees temporary variables, but my guess >> was that they are freed when the scope is left. > > Each variable has a refcount, then that hits 0 it can be freed up. To add to that. A zval will have a refcount, so if you do $a = someFunc(); then $a will have a refcount. If you do something like $a = someFunc(anotherFunc(moreFunc())), the return values of anotherFunc() and moreFunc() will be temp stored, but they will _not_ have a refcount because they never got assigned into a zval like $a. Hope that made sense. > >> >> If that is not true, then forget whatever I said. >> >> But if it is true, then there is no inherent difference between the >> two version. The only difference is that explicit $variables would >> need an entry in the active symbol table, which is pretty much >> negligible. >> >> -- >> PHP Internals - PHP Runtime Development Mailing List >> To unsubscribe, visit: http://www.php.net/unsub.php >>