Since PHP7.1, a foreach() expression can implement array destructuring as a way of unpacking row values and make individualized variable assignments.
When using array destructuring within a foreach() loop, can a specific value be accessed by its associative key more than once?
For example:
$array = [
['group' => 'A', 'name' => 'Ann', 'age' => 19],
['group' => 'B', 'name' => 'Bea', 'age' => 26],
['group' => 'A', 'name' => 'Cam', 'age' => 32],
['group' => 'B', 'name' => 'Des', 'age' => 24]
];
I know I can use:
foreach ($array as ['group' => $group, 'name' => $name, 'age' => $age]) {
// do stuff with $group, $name, and $age
}
But what if I want to access, say, $group a second time while destructuring? Is it possible?
It looks pretty unorthodox and there will be very few scenarios when it is useful, but yes it is possible/valid.
Just repeat the "key => value" syntax again and provide a different variable in the value position. In this context, the keys may be repeated.
Here is a demonstration of using array destructuring to "pivot" a result set with a body-less foreach loop.
Code: (Demo)
$array = [
['group' => 'A', 'name' => 'Ann', 'age' => 19],
['group' => 'B', 'name' => 'Bea', 'age' => 26],
['group' => 'A', 'name' => 'Cam', 'age' => 32],
['group' => 'B', 'name' => 'Des', 'age' => 24]
];
$result = [];
foreach ($array as ['group' => $group, 'group' => $result[$group]['group'], 'name' => $name, 'age' => $result[$group][$name]]);
# 1st assignment of group value^^^^^^
# 2nd assignment of group value-------------------^^^^^^^^^^^^^^^^^^^^^^^^
var_export($result);
Output:
array (
'A' =>
array (
'group' => 'A',
'Ann' => 19,
'Cam' => 32,
),
'B' =>
array (
'group' => 'B',
'Bea' => 26,
'Des' => 24,
),
)
The same technique works outside of the context of a foreach() loop as well. (Demo)
['one' => $result[], 'one' => $result[]] = ['one' => 1];
var_export($result);
Output:
array (
0 => 1,
1 => 1,
)