Regarding speed of foreach vs while(list) =each
I wrote a benchmark script and the results are that clearly foreach is faster. MUCH faster. Even with huge arrays (especially with huge arrays). I tested with sizes 100,000. 1,000,000 and 10,000,000. To do the test with 10 million i had to set my memory limit real high, it was close to 1gb by the time it actually worked. Anyways,
<?php
function getDiff($start, $end) {
$s = explode(' ', $start);
$stot = $s[1] + $s[0];
$e = explode(' ', $end);
$etot = $e[1] + $e[0];
return $etot - $stot;
}
$lim=10000000;
$arr = array();
for ($i=0; $i<$lim; $i++) {
$arr[$i] = $i/2;
}
$start = microtime();
foreach ($arr as $key=>$val);
$end = microtime();
echo "time for foreach = " . getDiff($start, $end) . ".\n";
reset($arr);
$start = microtime();
while (list($key, $val) = each($arr));
$end = microtime();
echo "time list each = " . getDiff($start, $end) . ".\n";
?>
here are some of my results: with 1,000,000
time for foreach = 0.0244591236115.
time list each = 0.158002853394.
desktop:/media/sda5/mpwolfe/tests$ php test.php
time for foreach = 0.0245339870453.
time list each = 0.154260158539.
desktop:/media/sda5/mpwolfe/tests$ php test.php
time for foreach = 0.0269000530243.
time list each = 0.157305955887.
then with 10,000,000:
desktop:/media/sda5/mpwolfe/tests$ php test.php
time for foreach = 1.96586894989.
time list each = 14.1371650696.
desktop:/media/sda5/mpwolfe/tests$ php test.php
time for foreach = 2.02504014969.
time list each = 13.7696218491.
desktop:/media/sda5/mpwolfe/tests$ php test.php
time for foreach = 2.0246758461.
time list each = 13.8425710201.
by the way, these results are with php 5.2 i believe, and a linux machine with 3gb of ram and 2.8ghz dual core pentium
each
(PHP 4, PHP 5, PHP 7)
each — 配列から現在のキーと値のペアを返して、カーソルを進める
警告
この関数は PHP 7.2.0 で 非推奨 になり、PHP 8.0.0 で 削除 されました。この関数に頼らないことを強く推奨します。
説明
配列から現在のキーと値のペアを返して、カーソルを進めます。
each() を実行した後、配列カーソルは、 配列の次の要素に移動します。配列の最終要素にカーソルがある場合は、 最終要素にとどまります。再度 each を使用して配列を走査するには、 reset() を使用する必要があります。
パラメータ
-
array -
入力の配列。
戻り値
配列 array から現在のキーと値のペアを返します。
このペアは 4 つの要素を持つ配列で、
それぞれの要素は 0, 1,
key, value というキーを有しています。
要素 0とkey
の各々は配列要素のキー名称を保持しており、1
と value の各々はそのデータを保持しています。
配列の内部ポインタが配列の最終要素以降を指す場合、
each() は false を返します。
例
例1 each() の例
<?php
$foo = array("bob", "fred", "jussi", "jouni", "egon", "marliese");
$bar = each($foo);
print_r($bar);
?>
$bar は、ここでは以下のキー/値のペアを保持しています。
Array
(
[1] => bob
[value] => bob
[0] => 0
[key] => 0
)
<?php
$foo = array("Robert" => "Bob", "Seppo" => "Sepi");
$bar = each($foo);
print_r($bar);
?>$bar は次のようなキー/値のペアを持つようになります。
Array
(
[1] => Bob
[value] => Bob
[0] => Robert
[key] => Robert
)
通常 each() は、配列の走査をするために list() と共に使用します。 例えばこのようになります。
例2 each() によって配列を走査する
<?php
$fruit = array('a' => 'apple', 'b' => 'banana', 'c' => 'cranberry');
reset($fruit);
while (list($key, $val) = each($fruit)) {
echo "$key => $val\n";
}
?>上の例の出力は以下となります。
a => apple b => banana c => cranberry
警告
配列を他の変数に代入すると、もとの配列の内部ポインタがリセットされます。 そのため、上の例のループ内で $fruit を他の変数に代入すると、無限ループを引き起こしてしまいます。
警告
each() をオブジェクトに対して使用することもできますが、 予期せぬ結果を返すことになるかもしれません。 オブジェクトのプロパティを each() で反復処理することはおすすめしません。
add a note
User Contributed Notes 25 notes
wolfeym38 at yahoo dot com ¶
17 years ago
phpcoder at gmail dot com ¶
5 years ago
each was deprecated because it exposed too much of the internal implementation details, blocking language development. ("We can't do X because it would break each().")
https://wiki.php.net/rfc/deprecations_php_7_2#each
If you want an array pointer, maintain it yourself. Probably a good idea anyway, because then it's visible in the code.
dmikam ¶
3 years ago
This function is marked as deprecated in PHP 7.2.0 and is removed in PHP 8.0.0, the replacement for legacy code would look like this:
function legacy_each($array){
$key = key($array);
$value = current($array);
$each = is_null($key) ? false : [
1 => $value,
'value' => $value,
0 => $key,
'key' => $key,
];
next($array);
return $each;
}
man13or at hotmail dot fr ¶
4 years ago
Hello, since each() and list() often "betray" very old applications, I simply recommend not to use them anymore.
If you want to assign variables based on an associative array,
Replace this:
while(list ($key, $value) = each ($my_array)) {
$$key = $value;
}
with this:
foreach ($my_array as $key => $value) {
$$key = $value;
}
sjoerd-php at linuxonly dot nl ¶
18 years ago
Use foreach instead of while, list and each. Foreach is:
- easier to read
- faster
- not influenced by the array pointer, so it does not need reset().
It works like this:
<?php
$arr = array('foo', 'bar');
foreach ($arr as $value) {
echo "The value is $value.";
}
$arr = array('key' => 'value', 'foo' => 'bar');
foreach ($arr as $key => $value) {
echo "Key: $key, value: $value";
}
?>
james at gogo dot co dot nz ¶
20 years ago
It's worth noting that references to an array don't have thier own array pointer, and taking a reference to an array doesn't reset it's array pointer, so this works as you would expect it would by eaching the first three items of the array, rather than the first item 3 times.
<?php
$x = array(1,2,3);
print_r(each($x));
echo "\n";
$y =& $x;
print_r(each($y));
echo "\n";
$z =& $y;
print_r(each($z));
echo "\n";
?>
Sopinon ¶
19 years ago
If you want to display the hole structure (tree) of your array, then you can use this recursive solution.
<?PHP
$tree= "";
array_tree($your_array);
echo $tree;
// Recursive Function
function array_tree($array, $index=0){
global $tree;
$space="";
for ($i=0;$i<$index;$i++){
$space .= " ";
}
if(gettype($array)=="array"){
$index++;
while (list ($x, $tmp) = each ($array)){
$tree .= $space."$x => $tmp\n";
array_tree($tmp, $index);
}
}
}
?>
Anonymous ¶
6 years ago
An odd function to deprecate. If you're keeping track of an array pointer in a collection outside a foreach loop you don't care about performance and the utility of this function is core.
Instead you must call two functions: current() and then next() to replicate its behaviour.
michael k (name der redaktion bekannt.) ¶
17 years ago
If you want to iterate over a two-dimensional, sparse array, and want to first display every first element, then every second and so on, you can use this code:
$fruits = array ( "fruits" => array ( "a" => "orange",
"b" => "banana",
"c" => "apple"
),
"numbers" => array ( 1,
2,
3,
4,
5,
6
),
"holes" => array ( "first",
5 => "second",
"third",
10 => "fourth",
)
);
$done = False;
while ($done == False) {
$done = True;
// Important: &$val has to be a reference (use the &),
// if you don't, the internal counter of $val will be
// re-initialized each time and you loop over the first elements
// for eternity.
foreach($fruits as $key => &$val) {
if (list($inner_key, $inner_val) = each(&$val)) {
$done = False;
echo "$key : : $inner_key => $inner_val <br> \n";
}
}
}
NOTE: this is just a quick hack, if you know a better way, post it!
janhsh ¶
1 year ago
Following the obsolescence of the each() function, here is a way to correct your source codes:
If you use each() in a while loop like this:
while (list($Key,$Value)=@each($Array)){
....
}
you have to replace with
foreach ($Array as $Key => $Value){
....
}
In the same minds.
while (list(,$Value)=@each($Array)){
....
}
will become
foreach ($Array as $Value){
....
}
matthew at mhalls dot net ¶
18 years ago
To panania at 3ringwebs dot com:
If you know for certain that you are only receiving one row, the while becomes redundant. To shorten your code:
$strSQL = "SELECT * FROM table WHERE id=1";
$RecordsetSelect = $db->runQuery ($strSQL);
list($key, $val) = mysql_fetch_row($RecordsetSelect);
echo "$key => $val\n";
mysql_free_result($RecordsetSelect);
With only one row being returned this is more elegant a solution, but just being nit-picky in essence. It also shows another quick way of using list.
Henk Poley ¶
5 years ago
Rector has an automated fix ('ListEachRector') to migrate away from `each()`:
https://github.com/rectorphp/rector/blob/master/docs/AllRectorsOverview.md#listeachrector
If you look at the code example you'll see this is even quite simple to do by hand.
massimo dot modica at tin dot it ¶
14 years ago
If you forget to reset the array before each(), the same code may give different results with different php versions.
<?php
$a = array(1,2,3);
foreach ($a AS $k => $v) $a[$k] = 2*$v;
while(list($k2, $v2) = each($a)) { echo($v2."\n"); }
?>
In PHP 5.2.0:
2
4
6
In PHP 5.2.6:
4
6
wodzuY2k at anronet dot pl ¶
22 years ago
This function will help you dump any variable into XML structure.
//dump var into simple XML structure
function var_dump_xml($tagname,$variable,$level=0)
{
for($i=0;$i<$level;$i++) $marg.=' ';
if (eregi('^[0-9].*$',$tagname)) $tagname='tag_'.$tagname; //XML tag cannot start with [0-9] character
if (is_array($variable))
{
echo $marg."<$tagname>\n";
while (list ($key, $val) = each ($variable)) var_dump_xml($key,$val,$level+1);
echo $marg."</$tagname>\n";
}
elseif (strlen($variable)>0)
{
echo $marg."<$tagname>".htmlspecialchars($variable)."</$tagname>\n";
};
};
/*
example:
$myVar = array("name"=>"Joe", "age"=>"26", "children"=>array("Ann","Michael"));
var_dump_xml("myVarTag",$myVar);
*/
amby2 at izh dot com ¶
18 years ago
I've found a compact way to cycle through an associative array using for statement (not while, as it has been done in the most of examples below):
<?php
for (reset($array); list($key) = each($array);) {
echo $key;
echo $array[$key];
}
?>
or
<?php
for (reset($array); list($key, $value) = each($array);) {
echo $key;
echo $value;
echo $array[$key];
}
?>
You hardly forget to add reset($array) code line using such construction.
tk at turtle-entertainment dot de ¶
23 years ago
Be sure to use the integrated functions "unset();" or "reset();" - many people forget this and wonder about the created output!
Anonymous ¶
22 years ago
I usually work a lot with 2D arrays. Since I've had some trouble traversing them correctly maybe someone out there also experienced those problems and can use this one.
It's based on a 2D-array called $array[$x][$y]. At some (but not necessarily all) (x,y) there is a value I want to reach. Note that I do not know beforehand the ranges of $x or $y (that is their highest and lowest values).
while (list ($x, $tmp) = each ($array)) {
while (list ($y, $val) = each ($tmp)) {
echo "$x, $y, $val";
}
}
The answer for each (x,y) pair can thus be (providng, of course those values where in your array beforehand):
1, 1, 2
2, 2, 0
3, 1, 1
5, 2, 2
5, 1, 2
Note that only the (x,y) pairs with a corresponding value is shown.
Hang in there
Jon Egil Strand
NTNU
Gillis at dancrea dot com ¶
22 years ago
I wrote a short and pretty simple script to search through associative arrays for some value in the values, heres a simplifyed example of it:
<?php
$foo['bob'] = "bob is ugly";
$foo['bill'] = "bill is rich";
$foo['barbie'] = "barbie is cute";
$search = "rich";
echo "searching the array foo for $search:<br>";
reset ($foo);
while (list ($key, $val) = each ($foo)) {
if (preg_match ("/$search/i", $val)) {
print "A match was found in $key.<br />";
} else {
print "A match was not found in $key.<br />";
}
}
?>
will output:
Searching the array foo for rich:
A match was not found in bob
A match was found in bill
A match was not found in barbie
13975001197 at 163 dot com ¶
6 years ago
In PHP 7.2 we can use foreach() to replace each(), such as:
foreach($array as $key => $value) {
//do something
}
gaviel ¶
13 years ago
Ok Here's one for iterating multidimensional array .. using foreach
<?php
$members = array(
"member1" => array (
"First Name" => "Robert",
"Last Name" => "Burton",
"Age" => "20"
),
"member2" => array (
"First Name" => "Cheska",
"Last Name" => "Vladesk",
"Age" => "21"
),
"member3" => array (
"First Name" => "Gino",
"Last Name" => "Marley",
"Age" => "19"
),
"member4" => array (
"First Name" => "Jake",
"Last Name" => "White",
"Age" => "16"
),
);
$dataSetCount = count($members);
echo "<h1>There are $dataSetCount members</h1>";
$i = 0;
foreach ($members as $each_members) {
$i++;
echo "<h2>Member $i</h2>";
foreach ($each_members as $position => $details) {
echo "<b>$position</b>" . ": " . $details . "<br />";
}
}
?>
php at omit dot ianco dot co dot uk ¶
16 years ago
I wanted to be able to add to an array while looping through it. foreach does not allow this because it is using a secret copy of the array. each makes this possible (tested on PHP 4).
<?php
$shopping_list = array('oysters', 'caviare');
reset ($shopping_list);
while (list($key, $value) = each ($shopping_list)) {
if ($value == 'oysters') $shopping_list[] = 'champagne';
elseif ($value == 'champagne') $shopping_list[] = 'ice';
}
print_r($shopping_list);
// Array ( [0] => oysters [1] => caviare [2] => champagne [3] => ice )
?>
kris at angelanthony dot com ¶
24 years ago
Remember to use "reset()" if you iterate over an array with "each()" more than once! Example:
while(list($key,$value) = each($array)){
// code here
}
NOW the internal pointer on $array is at the end of the array, and another attempt at an iteration like the one above will result in zero executions of the code within the "while" block. You MUST call "reset($array)" to reset the internal array pointer before iterating over the array again from the first element.
ayyappan dot ashok at gmail dot com ¶
8 years ago
/* Iterating using objects via each */
class SAI
{
public function __toString()
{
return __CLASS__;
}
}
$a = new SAI();
$b = new SAI();
$c = new SAI();
$d = new SAI();
$e = new SAI();
$objarray = array($a,$b,$c,$d,$e);
reset($objarray);
while (list($key, $val) = each($objarray))
{
echo "$key => $val\n";
}
//Results
0 => SAI
1 => SAI
2 => SAI
3 => SAI
4 => SAI
Warning:
each() will also accept objects, but may return unexpected results. It's therefore not recommended to iterate though object properties with each().
nino dot skopac at gmail dot com ¶
9 years ago
<?php
function each_v2($arr) {
// same as each() but when it hits end of array, it resets it
static $i = 0;
if (isset($arr[$i])) {
// exists¸
return $arr[$i++];
} else {
// reset $i to 0 and repeat
$i = 0;
return each_v2($arr);
}
}
?>
janhsh at tiscalinet dot be ¶
7 years ago
The following example is invalid in PHP 7 :
<?php
$fruit = array('a' => 'apple', 'b' => 'banana', 'c' => 'cranberry');
reset($fruit);
while (list($key, $val) = each($fruit)) {
echo "$key => $val\n";
}
?>
The correct writing is
<?php
$fruit = array('a' => 'apple', 'b' => 'banana', 'c' => 'cranberry');
reset($fruit);
while ($Item= each($fruit)) {
$key=$Item[0];
$val=$Item[1];
echo "$key => $val\n";
}
?>
This is because the "list ()" command on the left no longer works in PHP 7 and there is no replacement command.
Which is very deplorable because this command was strongly used and allowed in a simple way to assign variables from array.
