foreach

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 @.

Unpacking nested arrays

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.

<?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

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";
}

    

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";
}

    

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 ENTITY. In that case the value will be assigned by reference.

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

    

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

[!WARNING] A reference to the $value of the last array element remains even after the foreach loop. It is recommended to destroy it using unset. Otherwise, the following behavior will occur:

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

    

ENTITY

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

ENTITY

array

Traversable

iterable

list