## foreach

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

The `foreach` construct provides an easy way to iterate over arrays and Traversable objects. `foreach` will issue an error when used with a variable containing a different data type or with an uninitialized variable.

`foreach` can optionally get the `key` of each element:

    foreach (iterable_expression as $value) {
        statement_list
    }

    foreach (iterable_expression as $key => $value) {
        statement_list
    }

The first form traverses the iterable given by `iterable_expression`. On each iteration, the value of the current element is assigned to `$value`.

The second form will additionally assign the current element's key to the `$key` variable on each iteration.

Note that `foreach` does not modify the internal array pointer, which is used by functions such as current() and key().

It is possible to customize object iteration.

Example #1 Common `foreach` usages

`<?php
/* Example: value only */
$array = [1, 2, 3, 17];
foreach ($array as $value) {
echo "Current element of \$array: $value.\n";
}
/* Example: key and value */
$array = [
"one" => 1,
"two" => 2,
"three" => 3,
"seventeen" => 17
];
foreach ($array as $key => $value) {
echo "Key: $key => Value: $value\n";
}
/* Example: multi-dimensional key-value arrays */
$grid = [];
$grid[0][0] = "a";
$grid[0][1] = "b";
$grid[1][0] = "y";
$grid[1][1] = "z";
foreach ($grid as $y => $row) {
foreach ($row as $x => $value) {
echo "Value at position x=$x and y=$y: $value\n";
}
}
/* Example: dynamic arrays */
foreach (range(1, 5) as $value) {
echo "$value\n";
}
?>`

> Note:

> `foreach` does not support the ability to suppress error messages using the `@`.

### Unpacking nested arrays

(PHP 5 >= 5.5.0, PHP 7, PHP 8)

It is possible to iterate over an array of arrays and unpack the nested array into loop variables by using either array destructuring via `[]` or by using the list() language construct as the value.

> Note: Please note that array destructuring via `[]` is only possible as of PHP 7.1.0

In both of the following examples `$a` will be set to the first element of the nested array and `$b` will contain the second element:

`<?php
$array = [
[1, 2],
[3, 4],
];
foreach ($array as [$a, $b]) {
echo "A: $a; B: $b\n";
}
foreach ($array as list($a, $b)) {
echo "A: $a; B: $b\n";
}
?>`

The above example will output:

    A: 1; B: 2
    A: 3; B: 4

When providing fewer variables than there are elements in the array, the remaining elements will be ignored. Similarly, elements can be skipped over by using a comma:

`<?php
$array = [
[1, 2, 5],
[3, 4, 6],
];
foreach ($array as [$a, $b]) {
// Note that there is no $c here.
echo "$a $b\n";
}
foreach ($array as [, , $c]) {
// Skipping over $a and $b
echo "$c\n";
}
?>`

The above example will output:

    1 2
    3 4
    5
    6

A notice will be generated if there aren't enough array elements to fill the list():

`<?php
$array = [
[1, 2],
[3, 4],
];
foreach ($array as [$a, $b, $c]) {
echo "A: $a; B: $b; C: $c\n";
}
?>`

The above example will output:

    Notice: Undefined offset: 2 in example.php on line 7
    A: 1; B: 2; C:

    Notice: Undefined offset: 2 in example.php on line 7
    A: 3; B: 4; C:

### foreach and references

It is possible to directly modify array elements within a loop by preceding `$value` with `&`. In that case the value will be assigned by reference.

`<?php
$arr = [1, 2, 3, 4];
foreach ($arr as &$value) {
$value = $value * 2;
}
// $arr is now [2, 4, 6, 8]
unset($value); // break the reference with the last element
?>`
Warning

Reference to a `$value` of the last array element remain even after the `foreach` loop. It is recommended to destroy these using unset(). Otherwise, the following behavior will occur:

`<?php
$arr = [1, 2, 3, 4];
foreach ($arr as &$value) {
$value = $value * 2;
}
// $arr is now [2, 4, 6, 8]
// without an unset($value), $value is still a reference to the last item: $arr[3]
foreach ($arr as $key => $value) {
// $arr[3] will be updated with each value from $arr...
echo "{$key} => {$value} ";
print_r($arr);
}
// ...until ultimately the second-to-last value is copied onto the last value
?>`

The above example will output:

    0 => 2 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 2 )
    1 => 4 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 4 )
    2 => 6 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 6 )
    3 => 6 Array ( [0] => 2, [1] => 4, [2] => 6, [3] => 6 )

Example #2 Iterate a constant array's values by reference

`<?php
foreach ([1, 2, 3, 4] as &$value) {
$value = $value * 2;
}
?>`

### See Also

- array
- Traversable
- iterable
- list()

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