Count Array Value by Key - php

Question

Let say I have array like this :
Array (
[2015-03-14] => 3
[2015-05-23] => 10
[2015-06-21] => 7
[2015-05-24] => 3
[2015-06-27] => 10
[2015-06-29] => 7
)
Explanations :
The Key is for DATE and there are several different months and days ( 03 = March, 05 = May, etc )
Questions
How to count total of value based on the Key, for example someone set the date range field ( in frontend page ) and will get the total value from Key 2015-03-14 to 2015-06-27 ?
Or, is there any others method to make it more simple?

Answer 1

If you know your keys will always be dates, you can construct date objects using your keys and use date comparisons.
<?php
$arr = array(
'2015-03-14' => 3,
'2015-05-23' => 10,
'2015-06-21' => 7,
'2015-05-24' => 3,
'2015-06-27' => 10,
'2015-06-29' => 7,
);
$rangeStart = date('2015-03-14');
$rangeEnd = date('2015-06-27');
$sum = 0;
foreach ($arr as $key=>$value) {
$d = date($key);
if ($d >= $rangeStart && $d <= $rangeEnd) {
$sum += $arr[$key];
}
}
echo $sum;

Answer 2

First thing I have to ask, is do you have access to an SQL interface to get this information? Things like this are much better handled by SQL. The resulting code would perform better, be easier to understand and easier to write if you could just select only the entries you need from the database from the start.
Depending on your schema, the code might look like this (assuming PDO which you SHOULD be using):
$stmt = $db->prepare("
SELECT SUM(your_count_field)
FROM your_table
WHERE your_date_field BETWEEN '?' AND '?'
");
$result = $stmt->execute([$date_start, $date_end]);
In the absence of that, I don't think there's an easy way. #mittmemo has a pretty good solution, but I wouldn't use it if you have to select from more than 100 entries or so, or if you will one day need that kind of capacity.

Answer 3

If using PHP 5.6 or more,
$input = [
'2015-03-14' => 3,
'2015-05-23' => 10 ,
'2015-06-21' => 7 ,
'2015-05-24' => 3,
'2015-06-27' => 10 ,
'2015-06-29' => 7
];
$start_date = '2015-05-23';
$end_date = '2015-06-29';
$sum = array_sum(array_filter($input, function($date) use ($start_date, $end_date){
return ( ( $date >= $start_date ) && ( $date <= $end_date ) );
}, ARRAY_FILTER_USE_KEY));