list

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

listAssign variables as if they were an array

Опис

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

Like array(), this is not really a function, but a language construct. list() is used to assign a list of variables in one operation. Strings can not be unpacked and list() expressions can not be completely empty.

Зауваження:

Before PHP 7.1.0, list() only worked on numerical arrays and assumes the numerical indices start at 0.

Параметри

var

A variable.

vars

Further variables.

Значення, що повертаються

Returns the assigned array.

Журнал змін

Версія Опис
7.3.0 Support for reference assignments in array destructuring was added.
7.1.0 It is now possible to specify keys in list(). This enables destructuring of arrays with non-integer or non-sequential keys.

Приклади

Приклад #1 list() examples

<?php

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

// Listing all the variables
list($drink, $color, $power) = $info;
echo
"$drink is $color and $power makes it special.\n";

// Listing some of them
list($drink, , $power) = $info;
echo
"$drink has $power.\n";

// Or let's skip to only the third one
list( , , $power) = $info;
echo
"I need $power!\n";

// list() doesn't work with strings
list($bar) = "abcde";
var_dump($bar); // NULL
?>

Приклад #2 An example use of list()

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

Приклад #3 Using nested list()

<?php

list($a, list($b, $c)) = array(1, array(2, 3));

var_dump($a, $b, $c);

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

Приклад #4 list() and order of index definitions

The order in which the indices of the array to be consumed by list() are defined is irrelevant.

<?php
$foo
= array(2 => 'a', 'foo' => 'b', 0 => 'c');
$foo[1] = 'd';
list(
$x, $y, $z) = $foo;
var_dump($foo, $x, $y, $z);

Gives the following output (note the order of the elements compared in which order they were written in the list() syntax):

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"

Приклад #5 list() with keys

As of PHP 7.1.0 list() can now also contain explicit keys, which can be given as arbitrary expressions. Mixing of integer and string keys is allowed; however, elements with and without keys cannot be mixed.

<?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(
1 => $second, 3 => $fourth) = [1, 2, 3, 4];
echo
"$second, $fourth\n";

Поданий вище приклад виведе:

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

2, 4

Прогляньте також

  • each() - Return the current key and value pair from an array and advance the array cursor
  • array() - Create an array
  • extract() - Import variables into the current symbol table from an array

add a note

User Contributed Notes 24 notes

up
137
carlosv775 at gmail dot com
7 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
143
Rhamnia Mohamed
7 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
95
grzeniufication
9 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
megan at voices dot com
11 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
8
nek dot dev at gmail dot com
1 year ago
It can be convenient to specify a default value in case an element is missing in the list. You can use operator + for this:

<?php
$someArray
= ['color' => 'orange'];
[
'color' => $color, 'size' => $size] = $someArray + ['color' => null, 'size' => null];
?>

This will avoid the warning `Undefined array key "size"` you would encounter otherwise.
up
56
grzeniufication
7 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, $v4);
up
77
chris at chlab dot ch
11 years ago
The example states the following:
<?php
// list() doesn't work with strings
list($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
10
diyor024 at gmail dot com
3 years 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
38
pemapmodder1970 at gmail dot com
8 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
29
john at jbwalker dot com
10 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' $c='d'
up
7
vike2000 at gmail dot com
4 years ago
Setting it like <?php list($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
11 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
7
mark at manngo dot net
3 years 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
10
petru at fuxspam dot xtremeweb dot ro
6 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
5
samraskul at gmail dot com
3 years ago
list($a, $b, $c) = ["blue", "money", 32];

shortcut:

[$a, $b, $c] = ["blue", "money", 32];
up
7
blazej
7 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
5
Paul Marti
5 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
4
anthony dot ossent at live dot fr
7 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
3
contato at tobias dot ws
6 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
3
Colin Guthrie
9 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
-1
Mardaneus
6 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
-1
Dean
8 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
-1
fredsaavedra at hotmail dot com
4 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
5 years ago
As of PHP 7.3, lists now support array destructuring - see here: https://www.php.net/manual/en/migration73.new-features.php
To Top