PHP - Finding consecutive day counts in an array - php

Question

Let's say I have an array called $selectedDates containing the following
$selectedDates = [
"2000-01-31",
"2000-02-01",
"2000-02-02",
"2000-02-20"
];
Is there some way in PHP to calculate out what # each day is consecutively.
So that the first one returns 1, the 2nd one would be returning 2, the 3rd would be 3 but the 4th would be 1 again.
I'm trying to loop through them all at the moment but am not really getitng anywhere.
<?php foreach ($selectedDates as $date): ?>
Seriously lost about what to put here.
<?php echo $consecDayCount; ?>
<?php endforeach; ?>
I'm thinking inside of the loop I may need to loop through it again? And start at the first one and check each day going up one more, adding to some incrementer for each day that says the previous date in the array was the previous day in time. I'm just kind of banging my head against a wall figuring out that part.

Answer 1

One way to Rome...
# We assume $selectedDates is sorted at this point.
$selectedDates = [
"2000-01-31",
"2000-02-01",
"2000-02-02",
"2000-02-20"
];
# The array we will print.
$coll = array();
# We use array_reverse to start from the last entry.
foreach(array_reverse($selectedDates) as $date) {
$tmp = $date;
$con = 1;
do $tmp = date('Y-m-d', strtotime("$tmp -1day"));
# ++$con is used to count only up if in_array gives true.
while(in_array($tmp, $selectedDates) && (++$con));
$coll[$date] = $con;
}
print_r($coll);
Result: Array ( [2000-02-20] => 1 [2000-02-02] => 3 [2000-02-01] => 2 [2000-01-31] => 1 )

Answer 2

Here you go:
$selectedDates = [
'2000-01-31',
'2000-02-01',
'2000-02-02',
'2000-02-20',
'2000-02-21',
];
$format = 'Y-m-d';
$consecutive = [];
$length = count($selectedDates);
$streak = false;
$last = null;
for($index = 0; $index < $length - 1; $index++) {
$firstDate = DateTime::createFromFormat($format, $selectedDates[$index]);
$secondDate = DateTime::createFromFormat($format, $selectedDates[$index + 1]);
$diff = $firstDate->diff($secondDate);
if ($diff->days === 1) {
// consecutive dates
if ($streak) {
$consecutive[$last]++; // we have another consecutive day to the current streak
} else {
$consecutive[$selectedDates[$index]] = 2; // we already have 2 consecutive days
$last = $selectedDates[$index];
$streak = true;
}
} else {
$streak = false;
}
}
var_dump($consecutive);
This will give you an array in the date => number of consecutive days starting on that date format.

Answer 3

Another way
$dates = array(
new DateTime('2000-01-31'),
new DateTime('2000-02-01'),
new DateTime('2000-02-02'),
new DateTime('2000-02-20'),
);
// process the array
$lastDate = null;
$ranges = array();
$currentRange = array();
foreach ($dates as $date) {
if (null === $lastDate) {
$currentRange[] = $date;
} else {
// get the DateInterval object
$interval = $date->diff($lastDate);
// DateInterval has properties for
// days, weeks. months etc. You should
// implement some more robust conditions here to
// make sure all you're not getting false matches
// for diffs like a month and a day, a year and
// a day and so on...
if ($interval->days === 1) {
// add this date to the current range
$currentRange[] = $date;
} else {
// store the old range and start anew
$ranges[] = $currentRange;
$currentRange = array($date);
}
}
// end of iteration...
// this date is now the last date
$lastDate = $date;
}
// messy...
$ranges[] = $currentRange;
// print dates
foreach ($ranges as $range) {
// there'll always be one array element, so
// shift that off and create a string from the date object
$startDate = array_shift($range);
$str = sprintf('%s', $startDate->format('D j M'));
// if there are still elements in $range
// then this is a range. pop off the last
// element, do the same as above and concatenate
if (count($range)) {
$endDate = array_pop($range);
$str .= sprintf(' to %s', $endDate->format('D j M'));
}
echo "<p>$str</p>";
} ?>
output::: Mon 31 Jan to Wed 2 Feb
Sun 20 Feb