foreach
The foreach construct provides an easy way to
iterate over arrays. foreach works only on arrays
and objects, and will issue an error when you try to use it on a variable
with a different data type or an uninitialized variable. There are two
syntaxes:
$value)
statement
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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.
In order to be able to directly modify array elements within the loop precede
$value with &. In that case the value will be assigned by
reference.
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Reference of a $value and the last array element
remain even after the foreach loop. It is recommended
to destroy it by unset.
Otherwise you will experience the following behavior:
$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
// 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 )
?>
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It is possible to iterate a constant array's value by reference:
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foreach does not support the ability to
suppress error messages using
@.
Some more examples to demonstrate usage:
$v.\n";
$i++;
}
/* foreach example 3: key and value */
$a = array(
"one" => 1,
"two" => 2,
"three" => 3,
"seventeen" => 17
);
foreach ($a as $k => $v) {
echo "\$a[$k] => $v.\n";
}
/* foreach example 4: multi-dimensional arrays */
$a = array();
$a[0][0] = "a";
$a[0][1] = "b";
$a[1][0] = "y";
$a[1][1] = "z";
foreach ($a as $v1) {
foreach ($v1 as $v2) {
echo "$v2\n";
}
}
/* foreach example 5: dynamic arrays */
foreach (array(1, 2, 3, 4, 5) as $v) {
echo "$v\n";
}
?>
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Unpacking nested arrays with list()
It is possible to iterate over an array of arrays and unpack the
nested array into loop variables by providing a list
as the value.
For example:
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&example.outputs;
You can provide fewer elements in the list than there
are in the nested array, in which case the leftover array values will be
ignored:
]]>
&example.outputs;
A notice will be generated if there aren't enough array elements to fill
the list:
]]>
&example.outputs;