PHP combine two seperate conflicting date ranges into unique pairs

Question

Set one:

1. 2014-04-05 To 2014-06-27
2. 2014-06-28 To 2014-10-19

Set two:

1. 2014-04-05 To 2014-05-02
2. 2014-05-03 To 2014

Answer 1

Preparing

$arr1 = array(
  array('start'=>'2014-04-05', 'end'=> '2014-06-27'),
  array('start'=>'2014-06-28', 'end'=> '2014-10-19'),
);

$arr2 = array(
  array('start'=>'2014-04-05', 'end'=> '2014-05-02'),
  array('start'=>'2014-05-03', 'end'=> '2014-05-31'),
  array('start'=>'2014-06-01', 'end'=> '2014-10-21')
);

// merge arrays
$all = array_merge($arr1,$arr2);

// divide start-dates and end-dates into two arrays
$starts = array();
$ends = array();
foreach($all as $date){
    $starts[] = $date['start'];
    $ends[] = $date['end'];
}

// Remove duplicates and "sort ASC"
$starts = array_unique($starts);
natsort($starts);

$ends = array_unique($ends);
natsort($ends);

echo '
';
var_dump($starts,$ends);
echo '
';

output

array(4) {
    [0]=>
  string(10) "2014-04-05"
    [3]=>
  string(10) "2014-05-03"
    [4]=>
  string(10) "2014-06-01"
    [1]=>
  string(10) "2014-06-28"
}
array(5) {
    [2]=>
  string(10) "2014-05-02"
    [3]=>
  string(10) "2014-05-31"
    [0]=>
  string(10) "2014-06-27"
    [1]=>
  string(10) "2014-10-19"
    [4]=>
  string(10) "2014-10-21"
}

Ok. Now we need loop array $starts: for each start find closest end that more then start. Do it:

$ranges = array();

foreach($starts as $start){
    $start_time = strtotime($start);

    foreach($ends as $end){
        $end_time = strtotime($end);
        if ($start_time>$end_time) continue;
        else{
            $ranges[$end] = $start;
            break;
        }
    }
}

// "combine" 
$result = array();    
foreach($ranges as $end=>$start) {
    $result[] = array('start' => $start, 'end' => $end);
}

// print final result
foreach($result as $item){
    echo $item['start'].'  To  '.$item['end'].'
';
}

output:

2014-04-05 To 2014-05-02
2014-05-03 To 2014-05-31
2014-06-01 To 2014-06-27
2014-06-28 To 2014-10-19

What you need.

Note About this line in loops:

 $ranges[$end] = $start;

We can have this situation:

2014-04-03 To 2014-05-02
2014-04-04 To 2014-05-02
2014-04-05 To 2014-05-02

But it's wrong. Need only last range 2014-04-05 To 2014-05-02. And line:

 $ranges[$end] = $start;

override value with same key=> finally will be set proper 2014-04-05 to key 2014-05-02.