foreach

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

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

foreach (iterable_expression as $value) {
    statement_list
}

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

The first form traverses the value 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().

By default, an object is traversed over the properties that are visible from the current scope. It is possible to customize object iteration.

<?php

echo "Value only\n";
$array = [1, 2, 3, 17];

foreach ($array as $value) {
    echo "Current element of \$array: $value.\n";
}

echo "\n\nKey and value:\n";
$array = [
    "one" => 1,
    "two" => 2,
    "three" => 3,
    "seventeen" => 17
];

foreach ($array as $key => $value) {
    echo "Key: $key => Value: $value\n";
}

echo "\n\nMulti-dimensional key-value arrays:\n";
$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";
    }
}

echo "\n\nDynamic arrays:\n";
foreach (range(1, 5) as $value) {
    echo "$value\n";
}

Value only
Current element of $array: 1.
Current element of $array: 2.
Current element of $array: 3.
Current element of $array: 17.


Key and value:
Key: one => Value: 1
Key: two => Value: 2
Key: three => Value: 3
Key: seventeen => Value: 17


Multi-dimensional key-value arrays:
Value at position x=0 and y=0: a
Value at position x=1 and y=0: b
Value at position x=0 and y=1: y
Value at position x=1 and y=1: z


Dynamic arrays:
1
2
3
4
5

Note:

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

<?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";
}

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

<?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";
}

1 2
3 4
5
6

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

foreach ($array as [$a, $b, $c]) {
    echo "A: $a; B: $b; C: $c\n";
}

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:

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

array(4) {
  [0]=>
  int(2)
  [1]=>
  int(4)
  [2]=>
  int(6)
  [3]=>
  &int(8)
}

<?php
$arr = [1, 2, 3, 4];
foreach ($arr as &$value) {
    $value = $value * 2;
}
// $arr is now [2, 4, 6, 8]
var_dump($arr);

// without an unset($value), $value is still a reference to the last item: $arr[3]

echo "\nAnother loop:\n";
foreach ($arr as $key => $value) {
    // $arr[3] will be updated with each value from $arr...
    echo "{$key} => {$value}\n";
}
// ...until ultimately the second-to-last value is copied onto the last value
var_dump($arr);

array(4) {
  [0]=>
  int(2)
  [1]=>
  int(4)
  [2]=>
  int(6)
  [3]=>
  &int(8)
}

Another loop:
0 => 2
1 => 4
2 => 6
3 => 6
array(4) {
  [0]=>
  int(2)
  [1]=>
  int(4)
  [2]=>
  int(6)
  [3]=>
  &int(6)
}

<?php
foreach ([1, 2, 3, 4] as &$value) {
    $value = $value * 2;
    echo $value . "\n";
}

2
4
6
8