note 110545 deleted from language.references by aharvey

Note Submitter: jc (dot) flash (e-snail) gmail (dot) com ---- This is an important info, which I was missing untill today, so pay attention... Some people think that pass-by-reference speeds up your code, but that's not true... Lot of people know that references do NOT speed up your code, because PHP does copy-on-write... But what some people might not know (i didn't), is that references may actualy significantly SLOW your code DOWN, becouse they DISABLE copy-on-write. I couldn't believe it, so I tested it. (v. 5.3.10) <?php for($i=1;$i<100;$i++){ for($ii=1;$ii<1000;$ii++){ $arr[$i][$ii]=$i*$ii; } } $time=microtime(); ?> here we have two options 1) pass by value: <?php $foo=$arr; ?> 2) or pass by reference: <?php $foo=&$arr; ?> <?php for($i=1;$i<10000;$i++){ // paradox happens here.... // if $foo is reference, whole array is coppied $bar=$foo; } echo microtime()-$time; ?> They are both effectively pass-by-refference, because of copy-on-write. But next time, you assign this variable to another, paradox appears, because: In option 1), this second assign is pass-by-refference (because of copy-on-write) In option 2), this assign is actual COPY! (copy-on-write is disabled by forcing pass-by-refference before) results of microtime() are: 1) 0.002657 // without pass by refference 2) 0.064538 // with pass by refference Also, lot of built-in php functions (count for example) cannot work with reference, so if you use reference, they will make a real copy instead, again slowing your code down.