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list

(PHP 4, PHP 5, PHP 7, PHP 8)

list把数组中的值赋给一组变量

说明

list(mixed $var, mixed ...$vars = ?): array

array() 一样,这不是真正的函数,而是语言结构。 list() 可以在单次操作内为一组变量赋值。字符串不能解包且 list() 表达式不能完全为空。

注意:

在 PHP 7.1.0 之前的版本,list() 仅能用于数字索引的数组,并假定数字索引从 0 开始。

参数

var

一个变量。

vars

更多变量。

返回值

返回指定的数组。

更新日志

版本 说明
7.3.0 支持在数组解构时传引用。
7.1.0 现在可以指定 list() 中的键。 这就可以解构非数字键或者无顺序的数组。

范例

示例 #1 list() 例子

<?php

$info 
= array('coffee''brown''caffeine');

// 列出所有变量
list($drink$color$power) = $info;
echo 
"$drink is $color and $power makes it special.\n";

// 列出他们的其中一个
list($drink, , $power) = $info;
echo 
"$drink has $power.\n";

// 或者让我们跳到仅第三个
list( , , $power) = $info;
echo 
"I need $power!\n";

// list() 不能对字符串起作用
list($bar) = "abcde";
var_dump($bar); // NULL
?>

示例 #2 list() 用法的一个例子

<?php
$result 
$pdo->query("SELECT id, name FROM employees");
while (list(
$id$name) = $result->fetch(PDO::FETCH_NUM)) {
    echo 
"id: $id, name: $name\n";
}
?>

示例 #3 使用嵌套的 list()

<?php

list($a, list($b$c)) = array(1, array(23));

var_dump($a$b$c);

?>
int(1)
int(2)
int(3)

示例 #4 list() 和索引顺序定义

list() 使用 array 索引的顺序和它何时定义无关。

<?php
$foo 
= array(=> 'a''foo' => 'b'=> 'c');
$foo[1] = 'd';
list(
$x$y$z) = $foo;
var_dump($foo$x$y$z);

得到以下输出(注意比较 list() 所写的元素顺序):

array(4) {
  [2]=>
  string(1) "a"
  ["foo"]=>
  string(1) "b"
  [0]=>
  string(1) "c"
  [1]=>
  string(1) "d"
}
string(1) "c"
string(1) "d"
string(1) "a"

示例 #5 带键的 list()

从 PHP 7.1.0 开始,list() 可以包含显式的键,可赋值到任意表达式。 可以混合使用数字和字符串键。但是不能混合有键和无键不能混用。

<?php
$data 
= [
    [
"id" => 1"name" => 'Tom'],
    [
"id" => 2"name" => 'Fred'],
];
foreach (
$data as ["id" => $id"name" => $name]) {
    echo 
"id: $id, name: $name\n";
}
echo 
PHP_EOL;
list(
=> $second=> $fourth) = [1234];
echo 
"$second$fourth\n";

以上例程会输出:

id: 1, name: Tom
id: 2, name: Fred

2, 4

参见

  • each() - 返回数组中当前的键/值对并将数组指针向前移动一步
  • array() - 新建一个数组
  • extract() - 从数组中将变量导入到当前的符号表

add a note

User Contributed Notes 24 notes

up
138
Rhamnia Mohamed
5 years ago
Since PHP 7.1, keys can be specified

exemple :
<?php
$array
= ['locality' => 'Tunis', 'postal_code' => '1110'];

list(
'postal_code' => $zipCode, 'locality' => $locality) = $array;

print
$zipCode; // will output 1110
print $locality; // will output Tunis
?>
up
113
carlosv775 at gmail dot com
5 years ago
In PHP 7.1 we can do the following:

<?php
   
[$a, $b, $c] = ['a', 'b', 'c'];
?>

Before, we had to do:

<?php
   
list($a, $b, $c) = ['a', 'b''c'];
?>
up
86
grzeniufication
7 years ago
The example showing that:

$info = array('kawa', 'brązowa', 'kofeina');
list($a[0], $a[1], $a[2]) = $info;
var_dump($a);

outputs:
array(3) {
[2]=>
string(8) "kofeina"
[1]=>
string(5) "brązowa"
[0]=>
string(6) "kawa"
}

One thing to note here is that if you define the array earlier, e.g.:
$a = [0, 0, 0];

the indexes will be kept in the correct order:

array(3) {
  [0]=>
  string(4) "kawa"
  [1]=>
  string(8) "brązowa"
  [2]=>
  string(7) "kofeina"
}

Thought that it was worth mentioning.
up
77
chris at chlab dot ch
9 years ago
The example states the following:
<?php
// list() doesn't work with strings
list($bar) = "abcde";
var_dump($bar);
// output: NULL
?>

If the string is in a variable however, it seems using list() will treat the string as an array:
<?php
$string
= "abcde";
list(
$foo) = $string;
var_dump($foo);
// output: string(1) "a"
?>
up
53
grzeniufication
5 years ago
<?php
/**
* It seems you can skip listed values.
* Here's an example to show what I mean.
*
* FYI works just as well with PHP 7.1 shorthand list syntax.
* Tested against PHP 5.6.30, 7.1.5
*/
$a = [ 1, 2, 3, 4 ];

// this is quite normal use case for list
echo "Unpack all values\n";
list(
$v1, $v2, $v3, $v4) = $a;
echo
"$v1, $v2, $v3, $v4\n";
unset(
$v1, $v2, $v3, $v4);

// this is what I mean:
echo "Skip middle\n";
list(
$v1, , , $v4) = $a;
echo
"$v1, $v2, $v3, $v4\n";
unset(
$v1, $v2, $v3, $v4);

echo
"Skip beginning\n";
list( , ,
$v3, $v4) = $a;
echo
"$v1, $v2, $v3, $v4\n";
unset(
$v1, $v2, $v3, $v4);

echo
"Skip end\n";
list(
$v1, $v2, , ) = $a;
echo
"$v1, $v2, $v3, $v4\n";
unset(
$v1, $v2, $v3, $v4);

echo
"Leave middle\n";
list( ,
$v2, $v3, ) = $a;
echo
"$v1, $v2, $v3, $v4\n";
unset(
$v1, $v2, $v3, $v4);
up
65
megan at voices dot com
9 years ago
As noted, list() will give an error if the input array is too short. This can be avoided by array_merge()'ing in some default values. For example:

<?php
$parameter
= 'name';
list(
$a, $b ) = array_merge( explode( '=', $parameter ), array( true ) );
?>

However, you will have to array_merge with an array long enough to ensure there are enough elements (if $parameter is empty, the code above would still error).

An alternate approach would be to use array_pad on the array to ensure its length (if all the defaults you need to add are the same).

<?php
    $parameter
= 'bob-12345';
    list(
$name, $id, $fav_color, $age ) = array_pad( explode( '-', $parameter ), 4, '' );
   
var_dump($name, $id, $fav_color, $age);
/* outputs
string(3) "bob"
string(5) "12345"
string(0) ""
string(0) ""
*/
?>
up
3
diyor024 at gmail dot com
1 year ago
Don't miss simple array pattern matching since php 7

<?php

[$a] = ['hello!'];
var_dump($a); // 'hello!'

$arr = [4 => 50];
[
4 => $fifty] = $arr;
var_dump($fifty); // 50

$multidimensionalArray = [['id' => 15, 'email' => 'diyor024@gmail.com']];
[[
'id'  => $id, 'email' => $email]] = $multidimensionalArray;
var_dump($id, $email); // 15 diyor024@gmail.com

?>
up
33
pemapmodder1970 at gmail dot com
6 years ago
list() can be used with foreach

<?php
$array
= [[1, 2], [3, 4], [5, 6]];

foreach(
$array as list($odd, $even)){
    echo
"$odd is odd; $even is even", PHP_EOL;
}
?>

The output:
===
1 is odd; 2 is even
3 is odd; 4 is even
5 is odd; 6 is even
up
4
vike2000 at gmail dot com
2 years ago
Setting it like <?php list($var1,$varN) = null ?> does _not_ raise an E_NOTICE (or other error) and afaics effectively equals an https://php.net/function.unset of $var1,$varN.

I note this as contrasting with the fact that PHP triggers an E_NOTICE about "Undefined offset" "if there aren't enough array elements to fill the list()", as attow documented for https://php.net/control-structures.foreach#control-structures.foreach.list and here only noted in https://php.net/function.list#122951 by Mardaneus.

For completeness, a bash(1) (v5.0 or 4.3 on macos10.13) cli test producing the same result for all my PHP-versions (installed via macports.org) follows. It's also tested with php7.3 using bash5.0 on Debian10:
bash --noprofile --norc -c 'for php in php{{53..56},{70..73}};do for literal in "array()" null;do echo -n $php …=$literal:&&$php -n -d error_reporting=E_ALL -r "var_dump(list(\$var)=$literal);";done;done'

# Above produces the same result pairs per version from:
php53 …=array():
Notice: Undefined offset: 0 in Command line code on line 1
array(0) {
}
# ... to:
php73 …=null:NULL
up
48
svennd
9 years ago
The list() definition won't throw an error if your array is longer then defined list.
<?php

list($a, $b, $c) = array("a", "b", "c", "d");

var_dump($a); // a
var_dump($b); // b
var_dump($c); // c
?>
up
24
john at jbwalker dot com
8 years ago
The list construct seems to look for a sequential list of indexes rather taking elements in sequence. What that obscure statement means is that if you unset an element, list will not simply jump to the next element and assign that to the variable but will treat the missing element as a null or empty variable:

    $test = array("a","b","c","d");
    unset($test[1]);
    list($a,$b,$c)=$test;
    print "\$a='$a' \$b='$b' \$c='$c'<BR>";

results in:
$a='a' $b='' $c='c'

not:
$a='a' $b='c' $c='d'
up
4
mark at manngo dot net
1 year ago
For PHP 7.1 on, the documentation states that integer and string keys can be mixed, but that elements with and without keys cannot. Here is an example, using data from getimagesize() with mixed keys:

<?php
    $data
=[
       
0=> 160,
       
1 => 120,
       
2 => 2,
       
3 => 'width="160" height="120"',
       
'mime' => 'image/jpeg'
   
];
    list(
0=>$width,1=>$height,2=>$type,3=>$dimensions,'mime'=>$mime)=$data;
?>

Here, the numeric keys also need to be specified, as if the whole array is treated as an associative array.

As noted elsewhere, the list() operator can be written in array format:

<?php
   
[0=>$width,1=>$height,2=>$type,3=>$dimensions,'mime'=>$mime]=$data;
?>
up
5
petru at fuxspam dot xtremeweb dot ro
4 years ago
This is something I haven't seen in documentation.

Since PHP 7.1, you can use short-hand list unpacking using square brackets, just like short-hand array declaration:

<?php

$foo
= ['a', 'b', 'c'];

// short-hand array definition
[$a, $b, $c] = $foo;
echo
$a; // displays "a"

// it's same like:
list($x, $y, $z) = $foo;
echo
$x; // displays "a"

?>
up
4
Paul Marti
3 years ago
Since 7.1.0, you can use an array directly without list():

<?php
[$test, $test2] = explode(",", "hello, world");
echo
$test . $test2; // hello, world
?>
up
6
blazej
5 years ago
From PHP Version 7.1 you can specify keys in list(), or its new shorthand [] syntax. This enables destructuring of arrays with non-integer or non-sequential keys.

<?php
$data
= [
    [
"id" => 1, "name" => 'Tom'],
    [
"id" => 2, "name" => 'Fred'],
];

// list() style
list("id" => $id1, "name" => $name1) = $data[0];

// [] style
["id" => $id1, "name" => $name1] = $data[0];

// list() style
foreach ($data as list("id" => $id, "name" => $name)) {
   
// logic here with $id and $name
}

// [] style
foreach ($data as ["id" => $id, "name" => $name]) {
   
// logic here with $id and $name
}
up
4
contato at tobias dot ws
4 years ago
Since PHP 7.1 the [] may now be used as an alternative to the existing list() syntax:

<?php
[$number, $message] = explode('|', '123|Hello World!');
?>
up
4
anthony dot ossent at live dot fr
5 years ago
a simple example of use to swap two variables :

$a = 'hello';
$b = 'world';

list($a, $b) = [$b, $a];

echo $a . ' ' . $b; //display "world hello"

another example :

function getPosition($x, $y, $z)
{
   // ... some operations like $x++...
   return [$x, $y, $z];
}

list($x, $y, $z) = getPosition($x ,$y, $z);
up
1
Mardaneus
4 years ago
Unless you specify keys when using list() it expects the array being fed into it to start at 0.

So having the following code will result in a notice level warning "Undefined offset: 0" and variables not filling as expected

<?php
list($c1, $c2, $c3) = array [1 =>'a', 2 => 'b', 3 => 'c'];

var_dump($c1); // NULL
var_dump($c2); // string(1) "a"
var_dump($c3); // string(1) "b"

?>
up
2
Dean
6 years ago
UNDOCUMENTED BEHAVIOR:

    list($a,$b,$c) = null;

in fact works like:

    $a = null; $b = null; $c = null;

...So correspondingly:

    list($rows[]) = null;

Will increment count($rows), just as if you had executed $rows[] = null;

Watch out for this (for example) when retrieving entire tables from a database, e.g.

    while (list($rows[]) = $mysqlresult->fetch_row());

This will leave an extra 'null' entry as the last element of $rows.
up
2
samraskul at gmail dot com
1 year ago
list($a, $b, $c) = ["blue", "money", 32];

shortcut:

[$a, $b, $c] = ["blue", "money", 32];
up
0
Colin Guthrie
7 years ago
If you want use the undefined behaviour as you might expect it e.g. if you want:

  $b = ['a','b']; list($a, $b) = $b;

to result in $a=='a' and $b=='b', then you can just cast $b to an array (even although it already is) to create a copy. e.g.

  $b = ['a','b']; list($a, $b) = (array)$b;

and get the expected results.
up
-2
fredsaavedra at hotmail dot com
2 years ago
Easy way to get actual date and time values in variables.

list($day,$month,$year,$hour,$minute,$second) = explode('-',date('d-m-Y-G-i-s'));
echo "$day-$month-$year $hour".":".$minute.":".$second;
up
-5
JD
3 years ago
As of PHP 7.3, lists now support array destructuring - see here: https://www.php.net/manual/en/migration73.new-features.php
up
-3
sergey dot leonidovich dot shevchenko at gmail dot com
1 year ago
['a' => $x, 'b' => $y] = ['a' => 1, 'b' => 2];

echo $x . '-' . $y; // 1-2
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