在php中查找序列化日期的连续时间段

Question

I have the following array with dates in php:

Array ( 
  [0] => '2017-02-22'
  [1] => '2017-02-23'
  [2] => '2017-04-03'
  [3] => '2017-04-04'
  [4] => '2017-04-05'
  [5] => '2017-04-06'
)

Is there a way to find the continuous date periods included within the array?

For example for the above array the expected result would be:

2017-02-22 to 2017-02-23

and

2017-04-03 to 2017-04-06.

Thanks for your help!

Answer 1

There will be many ways to perform this task. Some that are harder to read than others. I'll list a few. I recommend using the first method for efficiency, and perhaps the third method for easy of output modification.

I have modified the sample data in the $dates array to show that it accommodates month changes, and stand-alone dates.

All of the following methods will assume that the dates are already sorted in ascending ordered. If not, then sort() will work on Y-m-d formatted dates; otherwise usort() will be neccessary.

My methods will take an array of dates like this:

$dates=[
  '2017-02-28',
  '2017-03-01',
  '2017-04-03',
  '2017-04-04',
  '2017-04-06',
  '2017-04-08',
  '2017-04-09',
  '2017-04-10'
];

And output this:

array (
  0 => '2017-02-28 to 2017-03-01',
  1 => '2017-04-03 to 2017-04-04',
  2 => '2017-04-06 to 2017-04-06',
  3 => '2017-04-08 to 2017-04-10',
)

Method #1: Single Foreach Loop (Demo)

foreach($dates as $date){
    if(!isset($start_date)){
        $start_date=$date;  // temporarily store new start date
    }elseif($date==date("Y-m-d",strtotime("$start_date +1 day")) || (isset($end_date) && $date==date("Y-m-d",strtotime("$end_date +1 day")))){
        $end_date=$date;    // temporarily store new or overwrite existing end date
    }else{
        $result[]="$start_date to ".(!isset($end_date)?$start_date:$end_date);  // current date is not in group, move temporary dates to result array
        $start_date=$date;  // overwrite previous start date
        unset($end_date);  // destroy previous end date
    }
}
$result[]="$start_date to ".(!isset($end_date)?$start_date:$end_date);  // move temporary dates to result array
var_export($result);

Method #2: Nested While Loops (Demo)

$copy=$dates;  // make a copy in case $dates is to be used again later
while($copy){  // iterate until the array is empty
    while(!isset($range) || current($copy)==date("Y-m-d",strtotime(substr($range,-10)." +1 day"))){  // iterate while date is new or consecutive
        $range=(!isset($range)?'':substr($range,0,10).' to ').array_shift($copy);  // temporarily store / overwrite the range data
    }
    $result[]=(strlen($range)==10?"$range to $range":$range);  // permanently store range data
    unset($range);  // destroy range string, for next iteration
}
var_export($result);

Method #3: Two Foreach Loops (Demo)

foreach($dates as $date){
    if(!isset($grouped)){  // first group
        $i=0;  // first group, index is zero
    }elseif($date!=date("Y-m-d",strtotime("$date_checker +1 day"))){  // if non-consecutive
        ++$i;  // next group, index is incremented
    }
    $grouped[$i][]=$date_checker=$date;  // store date as temporary date checker and into appropriate group
}

foreach($grouped as $group){
    $result[]=current($group)." to ".end($group);
}
var_export($result);

Or from the $grouped array in Method 3, you could simply alter the output structure to contain "range strings" as keys with subarrays holding the individual dates as elements using this:

foreach($grouped as $group){
    $result[current($group)." to ".end($group)]=$group;
}

Alternative Output:

array (
  '2017-02-28 to 2017-03-01' => 
  array (
    0 => '2017-02-28',
    1 => '2017-03-01',
  ),
  '2017-04-03 to 2017-04-04' => 
  array (
    0 => '2017-04-03',
    1 => '2017-04-04',
  ),
  '2017-04-06 to 2017-04-06' => 
  array (
    0 => '2017-04-06',
  ),
  '2017-04-08 to 2017-04-10' => 
  array (
    0 => '2017-04-08',
    1 => '2017-04-09',
    2 => '2017-04-10',
  ),
)