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Posted by Berimor on 12/04/05 00:34
On 3 Dec 2005 13:28:55 -0800, Chung Leong <chernyshevsky@hotmail.com>
wrote:
> Chameleon wrote:
>> THE QUESTION:
>> If I want a FAST script, I must use & everywhere? (e.g. foreach ($b as &
>> $v); )
>
> You should only use references when necessary, i.e. when you want the
> referenced variable to be modifed somewhere else down the line.
> Improper use of references will slow down your code considerably. For
> example, if you time the following loops, you'll find that the second
> one is much slower:
>
> //------------------first
> $t = microtime(true);
> for($z = 0; $z < 1000000; $z++) {
> $b = $a;
> $c = $b;
> }
>
> //------------------second
> $t = microtime(true);
> for($z = 0; $z < 1000000; $z++) {
> $b = $a;
> $c =& $b;
> }
>
> Why is the second loop slow?
To teach someone try it first by yourself!.
The first part (twice!!!!) slower then second one.
And do not compare C and PHP - its like to compare jet and aerostat.
Do try this code (but under php translator :) ) What will you say then?
<?
function getmicrotime(){
list($usec, $sec) = explode(" ",microtime());
return ((float)$usec + (float)$sec);
}
$a =
array(42,345,3245,3245,2345,4564,51346,3457234,13762,4561,3465,23,451,345,32,45,23,45,23,4,76,3,45,14,6,45632,46,32,4);
$a['ddd'] = array(345,34,532,45,3245,3,45,2345,7643345,2645612,6423,562);
//------------------first
$time_start = getmicrotime();
for($z = 0; $z < 1000000; $z++) {
$b = & $a['ddd'];// <--------- THIS LINE
$b = $a;
$c = $b;
}
$time_end = getmicrotime();
$time = $time_end - $time_start;
echo "$time\n ";
//------------------second
$time_start = getmicrotime();
for($z = 0; $z < 1000000; $z++) {
$b = $a;
$c = &$b;
}
$time_end = getmicrotime();
$time = $time_end - $time_start;
echo "$time\n";
?>
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