For a lot of people dates in PHP are an issue, and the PHP functions aren’t sufficient enough to do all converts you need.
Therefore you find a few easy PHP date conversion methods. Feel free to add your own methods or requests in the comments as we know that these methods don’t cover everything. You can see it for yourself when you read the rest of this entry:

• get start and end date for the next two months in an array
• get the datetime for a specific user culture in Symfony
• get all days between a given start and end date and return it in an array
• get the difference between two dates

1. get start and end date for the next two months in an array
   input: nothing
   output:
   array[0] = 1239706452
   array[1] = 1244976852
   *updated -> thx naholyr

   /**
    * get the next two months starting from today.
    *
    * @return array
    */
    public function getNextTwoMonths(){
    return array(time(), strtotime(’+2 month’));
    }
   

2. get the datetime for a specific user culture in Symfony
   input: 16/09/08
   output: 2008-09-16 23:35:55

    /**
    * Parses a date String from a specific culture to a Date.
    *
    * input example: 16/09/08
    *
    * returns: DateTime (Date)
    * @param String $period
    * @return Array of DateTime objects
    */
    public function parseDate($period) {
   
    $userCulture =  sfContext::getInstance()->getUser()->getCulture();
   
    $timestamp = sfContext::getInstance()->getI18N()->getTimestampForCulture($period, $userCulture);
   
    $period = new DateTime(date('Y-m-d H:i:s', $timestamp));
   
    return $period;
    }
   

3. get all days between a given start and end date and return it in an array.
   input: 2 DateTime dates
   output: array of days
   day[0] = 2008-12-10
   day[1] = 2008-12-11

   /**
    * With a given start and end date it will creates all the dates in between and return
    * it in an array.
    *
    * @param DateTime $startDate
    * @param DateTime $endDate
    * @return Array
    */
    public function getDaysByPeriod(DateTime $startDate, DateTime $endDate) {
   
    $startDt = clone $startDate;
   
    $days = array();
   
    while ( $startDt->format('U') <= $endDt->format('U') ) {
    $days[] = $startDt->format('Y-m-d');
    $startDt->modify("+1 days");
    }
   
    return $days;
    }
   

4. get the difference between two dates
   input:
   2009-04-14 10:08:35
   2009-04-15 10:10:35
   output: unix timestamp of the difference
   * updated -> thx Toni and David

   /**
    * get the difference between two dates
    *
    * @param date $firstTime
    * @param date $lastTime
    * @return integer
    */
   public function timeDiff($firstTime,$lastTime)
   {
    return strtotime($lastTime) - strtotime($firstTime);
   }
   

I struggled with a bit of code last week, but found a nice solution.

The goal was to convert 3 parameters into a date:

1. The day of the week (0 -> 6, 0 = Monday, 1 = Tuesday, 2 = Wednesday, etc.)
2. The week number (0 – 53, see our previous post for more info)
3. And the year (2009)

Well in this function we got to that result.

/**
* create datetime from dow, week number and year
* @param integer $dow (MUST BE 0 -> 6)
* @param integer $weekNumber
* @param integer $year
* @return datetime
*/
public function getDateTimeByDowWeekYear ($dow, $weekNumber, $year) {
// get the first day of the current year, according iso standards
$offset = date('w', mktime(0,0,0,1,1,$year));
$offset = ($offset < 5) ? 1-$offset : 8-$offset;
//get the first Monday of the year
$monday = mktime(0,0,0,1,1+$offset,$year);
//add the number of weeks
$mondayTime = strtotime('+' . ($weekNumber - 1) . ' weeks', $monday);
// add the number of weekdays
$dayTime = strtotime('+' . $dow . ' days', $mondayTime);
//create a date
return date('Y-m-d H:i:s',$dayTime);
}

It seemed to be a lot easier then I thought.
Et voila, have fun.