PHPBench.com runs quick benchmark scripts on each pageload. On the foreach test, when I load it, foreach takes anywhere from 4 to 10 times as long to run than the third example.
Why is it that a native language construct is apparently slower than performing the logic oneself?
分享 Maybe it has to do with the fact that foreach works on a copy of the array ?
Or maybe it has to do with the fact that, when looping with foreach, on each iteration, the internal array pointer is changed, to point to the next element ?
Quoting the relevant portion of foreach's manual page :
Note: Unless the array is referenced, foreach operates on a copy of the specified array and not the array itself. foreach has some side effects on the array pointer.
As far as I can tell, the third test you linked to doesn't do any of those two things -- which means both tests don't do the same thing -- which means you are not comparing two way of writing the same code.
(I would also say that this kind of micro-optimization will not matter at all in a real application -- but I guess you already know that, and just asked out of curiosity)
There is also one thing that doesn't feel right in this test : it only does the test one time ;; for a "better" test, it might be useful to test all of those more than once -- with timings in the order of 100 micro-seconds, not much is required to make a huge difference.
(Considering the first test varies between 300% and 500% on a few refreshes...)
For those who don't want to click, here's the first test (I've gotten 3xx%, 443%, and 529%) :
foreach($aHash as $key=>$val) {
$aHash[$key] .= "a";
}
And the third one (100%) :
$key = array_keys($aHash);
$size = sizeOf($key);
for ($i=0; $i<$size; $i++) {
$aHash[$key[$i]] .= "a";
}
