(PHP 5 >= 5.3.0)
DatePeriod::__construct — Creates a new DatePeriod object
$start
   , DateInterval $interval
   , int $recurrences
   [, int $options
  ] )$start
   , DateInterval $interval
   , DateTime $end
   [, int $options
  ] )$isostr
   [, int $options
  ] )Creates a new DatePeriod object.
start
     The start date of the period.
interval
     The interval between recurrences within the period.
recurrences
     The number of recurrences.
end
     The end date of the period.
isostr
     An ISO 8601 repeating interval specification.
options
     
       Can be set to DatePeriod::EXCLUDE_START_DATE to
       exclude the start date from the set of recurring dates within the
       period.
      
Example #1 DatePeriod example
<?php
$start = new DateTime('2012-07-01');
$interval = new DateInterval('P7D');
$end = new DateTime('2012-07-31');
$recurrences = 4;
$iso = 'R4/2012-07-01T00:00:00Z/P7D';
// All of these periods are equivalent.
$period = new DatePeriod($start, $interval, $recurrences);
$period = new DatePeriod($start, $interval, $end);
$period = new DatePeriod($iso);
// By iterating over the DatePeriod object, all of the
// recurring dates within that period are printed.
foreach ($period as $date) {
    echo $date->format('Y-m-d')."\n";
}
?>
The above example will output:
2012-07-01 2012-07-08 2012-07-15 2012-07-22 2012-07-29
Example #2 DatePeriod example with DatePeriod::EXCLUDE_START_DATE
<?php
$start = new DateTime('2012-07-01');
$interval = new DateInterval('P7D');
$end = new DateTime('2012-07-31');
$period = new DatePeriod($start, $interval, $end,
                         DatePeriod::EXCLUDE_START_DATE);
// By iterating over the DatePeriod object, all of the
// recurring dates within that period are printed.
// Note that, in this case, 2012-07-01 is not printed.
foreach ($period as $date) {
    echo $date->format('Y-m-d')."\n";
}
?>
The above example will output:
2012-07-08 2012-07-15 2012-07-22 2012-07-29