Thnaks for an explanation. Rasmus Lerdorf <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > This has been explained a few times. PHP does shallow copies, or > copy-on-write which means that the data is not actually copied until you > change it. That is: > > $a = "1234567890"; > $b = $a; > > internally we do not copy the data from $a to $b until you change $b. > > We you use references we have a bit more work to do as we need to decouple > this and indicate that copy-on-write should not be taking place. > > Basically things are optimized for the most common case. > > -Rasmus > > On Tue, 8 Oct 2002, Markas wrote: > > > I tried some trivial expirements: > > > > /* here I define an array $big, which I guess would "eat" ~100kb of memory */ > > for($i=0; $i<10000; $i++) > > { > > $big[$i] = "1234567890"; > > } > > > > /* this func only returns the value it gets as a param...*/ > > function f($a){return $a;} > > > > $start = microtime(); > > > > /* here all the job is done */ > > for ($i=0; $i < 100; $i++){$a = f($big);} /* <--- every iteration I just pass $big array to this func and it simply returns it*/ > > > > $end = microtime(); > > > > /* here I find out the time the job above takes to run, similar to the code from the help:*/ > > function getmicrotime($time){ > > list($usec, $sec) = explode(" ",$time); > > return ((float)$usec + (float)$sec); > > } > > > > $time_start = getmicrotime($start); > > $time_end = getmicrotime($end); > > $time = $time_end - $time_start; > > > > echo "Did nothing in $time seconds"; > > > > So the script above takes on my server ~0.00115 sec, so as far as I understand, it takes php to copy that $big array which is rather large, at least 100 times... So I decided to change the function f($a): > > function f($a){return $a;} changed to function f(&$a){return $a;}, > > as you can see, I only wanted to pass that $a param by reference, without copying it, so I thought I win in performance and the 100 iterations will work faster, as no copying of such a large array $big (which is this time going to be passed by refernce) will be involved,... BUT this case the job took ~3.75093 seconds, which is 3262 times SLOWER !!! I also found out, that while using refernces, the time of job's run strictly depends on the $big array dimension, and while NOT using references, the time doesn't depend on that, but I thought just on the contrary. I thought, that while using references, we dont copy the data and therefore do not depend on that data amount, but the example above shows just the opposite results... > > > > What's going on, if anybody gets interested, please explain? > > >
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