(PHP 4, PHP 5, PHP 7, PHP 8)
The foreach construct provides an easy way to
iterate over array s 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:
foreachdoes not support the ability to suppress error messages using the@.
(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
$array = [
[1, 2, 3],
[3, 4, 6],
];
foreach ($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:
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
?>
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;
}
?>An easier way to unpack nested array elements
$array = [
[1, 2],
[3, 4],
];
foreach ($array as [$a, $b]) {
echo "A: $a; B: $b\n";
}