Easily create a collection of dates within range of two dates.

DateRange.php

<?php

namespace App\Support;

use ArrayIterator;
use Countable;
use DatePeriod;
use DateTime;
use DateInterval;
use IteratorAggregate;
use Illuminate\Support\Carbon;

class DateRange implements IteratorAggregate, Countable
{
   /**
    * The start of the date range.
    * 
    * @var \DateTime
    */
   protected $starts_at;

   /**
    * The end of the date range.
    * 
    * @var \DateTime
    */
   protected $ends_at;

   /**
    * The space between the dates.
    * 
    * @var \DateInterval
    */
   protected $interval;

   /**
    * The date format.
    * 
    * @var string
    */
   protected $format = 'Y-m-d';

   /**
    * Key of the dates.
    * 
    * @var string
    */
   protected $keyedBy;

   /**
    * Construct the DateRange.
    * 
    * @param  string|null          $starts_at [defaults to now.]
    * @param  string|null          $ends_at [defaults to end of year.]
    * @param  string|null          $interval [The interval between each date.]
    */
   public function __construct($starts_at = null, $ends_at = null, $interval = null)
   {
      $this->startsAt($starts_at ?: Carbon::now());
      $this->endsAt($ends_at ?: Carbon::now()->endOfYear());
      $this->interval($interval ?: '1 day');
   }

   /**
    * Delegate calls to the underlying collection.
    * 
    * @param  string $method     
    * @param  array  $parameters 
    * @return mixed | \Illuminate\Support\Collection
    */
   public function __call($method, $parameters = [])
   {
      return $this->create()->$method(...$parameters);
   }

   /**
    * Delegate undefined attributes to the underyling Collection.
    * 
    * @param  string $key 
    * @return mixed
    */
   public function __get($key)
   {
      if (property_exists($this, $key)) {
         return $this->$key;
      }

      return $this->create()->$key;
   }

   /**
    * Assign a key for each of the dates
    * 
    * @param  string $key 
    * @return $this
    */
   public function keyedBy(string $key)
   {
      $this->keyedBy = $key;

      return $this;
   }

   /**
    * The date format
    * 
    * @param  string $format
    * @return $this
    */
   public function format(string $format)
   {
      $this->format = $format;

      return $this;
   }

   /**
    * Set the start date 
    * 
    * @param string|\DateTime $date 
    * @return $this
    */
   public function startsAt($date)
   {
      $this->starts_at = Carbon::parse($date);

      return $this;
   }

   /**
    * Set the end date 
    * 
    * @param string|\DateTime $date 
    * @return $this
    */
   public function endsAt($date)
   {
      $this->ends_at = Carbon::parse($date);

      return $this;
   }   

   /**
    * Set the date interval
    * 
    * @param  \DateInterval | string $value
    * @return $this
    */
   public function interval($value)
   {
      if (is_string($value)) {
         $this->interval = DateInterval::createFromDateString($value);
      } else {
         $this->interval = $value;
      }

      return $this;
   }

   /**
    * Create the dateRange collection
    * 
    * @return \Illuminate\Support\Collection
    */
   public function create()
   {
      $dates = $this->formatDates($this->dates());

      $results = $this->assignKeyToDates($dates);

      return collect($results);
   }

   /**
    * Get the raw date array
    * 
    * @return array
    */
   public function dates()
   {
      return iterator_to_array(new DatePeriod($this->starts_at, $this->interval, $this->ends_at));
   }

   /**
    * Get the iterator from the collection
    * 
    * @return \ArrayIterator
    */
   public function getIterator()
   {
      return $this->create()->getIterator();
   }

   /**
    * Count the total number of dates.
    *
    * @return int
    */
   public function count()
   {
      return count($this->dates());
   }

   /**
    * Format the DateTime objects into strings.
    * 
    * @param  array  $range 
    * @return array
    */
   protected function formatDates(array $range)
   {
      if (blank($this->format)) {
         return $range;
      }

      return array_map(function ($date) {
         return $date->format($this->format);
      }, $range);
   }

   /**
    * Assign the key to each of the dates
    * 
    * @param  array  $dates 
    * @return array
    */
   protected function assignKeyToDates(array $dates)
   {
      if (blank($this->keyedBy)) {
         return $dates;
      }

      $results = [];

      foreach ($dates as $date) {
         $results[] = [$this->keyedBy => $date];
      }

      return $results;
   }
}