Here's what I'm doing:
$dateRange = array('2010-01-01', '2010-01-02', '2010-01-03', ...);
$data = array('2010-01-01' => 5, '2010-01-03' => 7);
foreach ($dateRange as $date) {
$values[$date] = $data[$date];
}
$values results in:
array (
'2010-01-01' => 5
'2010-01-02' => null
'2010-01-03' => 7
...
)
Seems fairly efficient, but I wonder if there's a simple PHP function that'll handle this.
$values = array_merge(array_fill_keys($dateRange, null), $data);
Whether that's really any more efficient can only be found out through testing, but I'd say it's more concise, easy to understand, and it doesn't throw errors for non-existent keys in $data. :)
array_merge says: If the input arrays have the same string keys, then the later value for that key will overwrite the previous one. I'm using array_merge daily, and this is how it works. Also, these are clearly string keys, not numeric keys.array_merge keeping the sort order intact though. :) You have a point about changing the keys to day numbers, but at that point it'd submit you're talking about a completely different script and would need to reevaluate every operation you're doing on the array anyway. There's no need to go out of your way to make sure your script is internally future-proof. ;) So, just for the record: $values = $data + array_fill_keys($dateRange, null) should work the same, except for the order of the result.There's array_merge but it will produce 1 => 2010-01-02 instead of 2010-01-02 => null.
There are also a whole host of array functions at http://us.php.net/manual/en/ref.array.php
[Edit]: Leaving this answer because of the links, but the other answer accomplishes exactly what you wanted.
To populate the desired associative array in a single pass, you can use array_reduce() and fallback to null values when a date doesn't have a related value in $data. Because this associative array doesn't have numeric keys, the union operator can be used to add new elements to the result array. Demo
var_export(
array_reduce(
$dateRange,
fn($result, $date) => $result + [$date => $data[$date] ?? null],
[]
)
);
Or another way it to combine the dates array with the null coalesced array. Demo
var_export(
array_combine(
$dateRange,
array_map(fn($date) => $data[$date] ?? null, $dateRange)
)
);
There's also nothing unprofessional about using a classic loop, just make sure to null coalesce to avoid Warnings. Demo
$result = [];
foreach ($dateRange as $date) {
$result[$date] = $data[$date] ?? null;
}
var_export($result);