list
list
(PHP 4, PHP 5, PHP 7)
list — Assign variables as if they were an array
Description
array list ( mixed $var1 [, mixed $... ] )
Like array(), this is not really a function, but a language construct. list() is used to assign a list of variables in one operation.
Note:
list() only works on numerical arrays and assumes the numerical indices start at 0.
In PHP 5, list() assigns the values starting with the right-most parameter. In PHP 7, list() starts with the left-most parameter.
If you are using plain variables, you don't have to worry about this. But if you are using arrays with indices you usually expect the order of the indices in the array the same you wrote in the list() from left to right, which is not the case in PHP 5, as it's assigned in the reverse order.
Generally speaking, it is advisable to avoid relying on a specific order of operation, as this may change again in the future.
Modification of the array during list() execution (e.g. using list($a, $b) = $b) results in undefined behavior.
Parameters
-
var1
-
A variable.
Return Values
Returns the assigned array.
Changelog
Version | Description |
---|---|
7.0.0 | The order that the assignment operations are performed in has changed. |
7.0.0 | list() expressions can no longer be completely empty. |
7.0.0 | Strings can no longer be unpacked. |
Examples
Example #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 ?>
Example #2 An example use of list()
<table> <tr> <th>Employee name</th> <th>Salary</th> </tr> <?php $result = $pdo->query("SELECT id, name, salary FROM employees"); while (list($id, $name, $salary) = $result->fetch(PDO::FETCH_NUM)) { echo " <tr>\n" . " <td><a href=\"info.php?id=$id\">$name</a></td>\n" . " <td>$salary</td>\n" . " </tr>\n"; } ?> </table>
Example #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)
Example #4 Using list() with array indices
<?php $info = array('coffee', 'brown', 'caffeine'); list($a[0], $a[1], $a[2]) = $info; var_dump($a); ?>
Gives the following output (note the order of the elements compared in which order they were written in the list() syntax):
Output of the above example in PHP 7:
array(3) { [0]=> string(6) "coffee" [1]=> string(5) "brown" [2]=> string(8) "caffeine" }
Output of the above example in PHP 5:
array(3) { [2]=> string(8) "caffeine" [1]=> string(5) "brown" [0]=> string(6) "coffee" }
Example #5 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"
See Also
© 1997–2017 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
https://secure.php.net/manual/en/function.list.php