Is the copy of an array for a foreach (of php5, in this case) an immediate copy with actual overhead, or merely a lazy copy (copy on write) which only produces overhead if it detects a write manipulation?
The alternative, note in several places, is to run foreach over keys($array) -- how can that really be faster?
OK, so I went off and measured it --
Test This And This And, uh, This
--------------------------- ---------------------------- ----------------------------
Setup Setup Setup
---------------------------- ---------------------------- ----------------------------
$i = array_fill(0,1000, 1 ); $j = array_fill(0,1000, 1 ); $j = array_fill(0,1000, 1 );
$c = 0; $d = 0; $e = 0;
--------------------------- ---------------------------- ---------------------------
Code Under Test Code Under Test Code Under Test
--------------------------- ------------------------------ --------------------------
foreach ($i as $v) foreach (array_keys($j) as $k) foreach ($i as &$v)
{ $c+= $v; } { $d+= $j[$k]; } { $e+= $v; }
--------------------------- ------------------------------ -------------------------
Tear Down Tear Down Tear Down
--------------------------- ----------------------------- -------------------------
print "c = $c"; print "d = $d"; print "e = $e";
---------------------------- ----------------------------- --------------------------
Test for repetitions. 10000
---------------------------- ----------------------------- -------------------------
c = 10000000 d = 10000000 e = 10000000
---------------------------- ----------------------------- -------------------------
Ran in 1.8540189266205 Ran in 4.0039160251617 Ran in 1.9633851051331
--------------------------- ----------------------------- -------------------------
Winner -0.10936617851257 Looser 2.0405309200287 2nd Best 0
--------------------------- ---------------------------- -------------------------
Looks like foreach ($a as $v) is much better than array_keys and that using &v is in the middle.
PHP uses copy-on-write. It s slower to pass by reference because it has to setup the data structures to maintain the reference.
OK, here is the other requested comparison (what do you think?)
Test This And This
--------------------------------------- --------------------------------------
Setup Setup
-------------------------------------- --------------------------------------
$k = array_fill(0,1000, 1 ); $i = array_fill(0,1000, 1 );
$f = 0; $c = 0;
$kMax = count($k);
-------------------------------------- --------------------------------------
Code Under Test Code Under Test
-------------------------------------- --------------------------------------
for ($x = 0; $x < kiMax; $x++) foreach ($i as $v)
{ $f+= $k[$x]; } { $c+= $v; }
-------------------------------------- --------------------------------------
Tear Down Tear Down
-------------------------------------- --------------------------------------
print "f = $f"; print "c = $c";
-------------------------------------- --------------------------------------
Test for repetitions: 10,000
-------------------------------------- --------------------------------------
f = 10000000 c = 10000000
-------------------------------------- --------------------------------------
Ran in 2.8563051223755 Ran in 1.8667521476746
-------------------------------------- -------------------------------------
2nd best 0.98955297470093 Winner 0
I am trying to write a script to prevent brute-force login attempts in a website I m building. The logic goes something like this: User sends login information. Check if username and password is ...
<?php $con=mysql_connect("localhost","mts","mts"); if(!con) { die( unable to connect . mysql_error()); } mysql_select_db("mts",$con); /* date_default_timezone_set ("Asia/Calcutta"); $date = ...
I found this script online that creates a thumbnail out of a image but the thumbnail image is created with poor quality how can I improve the quality of the image. And is there a better way to create ...
如何确认来自正确来源的数字。
Most sites need some way to show the dates on the site in the users preferred timezone. Below are two lists that I found and then one method using the built in PHP DateTime class in PHP 5. I need ...
I wonder there is a way to post a message to a facebook business page with cURL? thanks
I want to create text as a watermark for an image. the water mark should have the following properties front: Impact color: white opacity: 31% Font style: regular, bold Bevel and Emboss size: 30 ...
How does php cast boolean variables? I was trying to save a boolean value to an array: $result["Users"]["is_login"] = true; but when I use debug the is_login value is blank. and when I do ...