[TYPO3-dev] FYI: comparing execution speed of some php functions

[Rupert Germann]

hi devs,

I've read a lot of articles about performance in webapplications during the
last days and stumbled (again) upon questions like: 
is is_array() faster than count()? or how much faster is foreach() compared
to while(list()...)? 
and many more.

to get some reliable results I wrote a little test script which you can
download here http://rgdata.de/fileadmin/typo3_dev/speed_test.php.txt 

The script iterates through a big array with 100000 entries and measures the
execution time of certain operations.

here are some of the results:

for() loop:
---------------------------------------------
for() loop using count() took           20.86401 ms 
for() loop Not using count() took       7.09796 ms

using count() means: 
for ($i = 1; $i < count($myarr); ++ $i) {...

OK, I think that should not be a new information for anyone here ;-) 
but what about while and foreach?

foreach() loop:
---------------------------------------------
foreach() took                  11.16920 ms
foreach() with KEY took         12.35318 ms

while(list()=each()) loop:
---------------------------------------------
while(list()...) took           58.12597 ms
while(list()...) with key took  64.06283 ms


interesting, isn't it?
That means even if I have something like this in my code:

while(list($key) = each($arr)) {
  // do smthg that needs only $key
}
 
it will be way slower than:

foreach($arr as $key => $val) {
  // do smthg that needs only $key
}

although $val is never used.

If I count the occurences of "while(list(" in class tslib_content I see some
potential here.

(FYI: the patch for class tslib_content is almost ready)

another interesting question: are statically called methods faster or those
from instantiated objects?

calling methods in classes:
---------------------------------------------
object call took                40.79103 ms
derived object call took        40.16995 ms
static call took                102.13280 ms

hmm, until now I thought it is exactly the other way round. Could someone
plaese have a look to my testscript and tell me if this behaviour is caused
by my testing method. strange.


next test: accessing array vars

let's say we have a piece of code like this:
function arraytest($num) {
        for ($i = 0; $i < $num; ++ $i) {
                if ($GLOBALS['foo']['bar'] == "test") {
                        $j = 1;
                } else {
                        $j = FALSE;
                }
        }
}

quite common in TYPO3 source - e.g. all those checks involving
$GLOBALS['TYPO3_CONF_VARS']...

if we now change the code like below it will run faster:

function arraytest2($num) {
        $testvar = $GLOBALS['foo']['bar'];
        for ($i = 0; $i < $num; ++ $i) {
                if ($testvar == "test") {
                        $j = 1;
                } else {
                        $j = FALSE;
                }
        }
}

results:
---------------------------------------------
accessing array took                    21.87395 ms 
accessing local var took                13.07201 ms 


the script speed_test.php makes some more tests e.g. measuring the speed of
different string comparing methods.

If you know some commonly used code constructs that can be substituted by
faster variants - let me know!

happy benchmarking!

greets 
rupert


further reading:
http://www.tuxradar.com/practicalphp/18/0/0
http://phplens.com/lens/php-book/optimizing-debugging-php.php