Question

How do you actually perform datetime operations such as adding date, finding difference, find out how many days excluding weekends in an interval? I personally started to pass some of these operations to my postgresql dbms as typically I would only need to issue one sql statement to obtain an answer, however, to do it in PHP way I would have to write a lot more code that means more chances for errors to occur…

Are there any libraries in PHP that does datetime operation in a way that don’t require a lot of code? that beats sql in a situation where ‘Given two dates, how many workdays are there between the two dates? Implement in either SQL, or $pet_lang’ that is solved by making this query?

SELECT  COUNT(*) AS total_days FROM    (SELECT date '2008-8-26' + generate_series(0,           (date '2008-9-1' - date '2008-8-26')) AS all_days) AS calendar WHERE   EXTRACT(isodow FROM all_days) < 6; 

Answer 1

PHP5+’s DateTime object is useful because it is leap time and daylight savings aware, but it needs some extension to really solve the problem. I wrote the following to solve a similar problem. The find_WeekdaysFromThisTo() method is brute-force, but it works reasonably quickly if your time span is less than 2 years.

$tryme = new Extended_DateTime('2007-8-26'); $newer = new Extended_DateTime('2008-9-1');  print 'Weekdays From '.$tryme->format('Y-m-d').' To '.$newer->format('Y-m-d').': '.$tryme -> find_WeekdaysFromThisTo($newer) .'\n'; /*  Output:  Weekdays From 2007-08-26 To 2008-09-01: 265  */ print 'All Days From '.$tryme->format('Y-m-d').' To '.$newer->format('Y-m-d').': '.$tryme -> find_AllDaysFromThisTo($newer) .'\n'; /*  Output:  All Days From 2007-08-26 To 2008-09-01: 371   */ $timefrom = $tryme->find_TimeFromThisTo($newer); print 'Between '.$tryme->format('Y-m-d').' and '.$newer->format('Y-m-d').' there are '.       $timefrom['years'].' years, '.$timefrom['months'].' months, and '.$timefrom['days'].       ' days.'.'\n'; /*  Output: Between 2007-08-26 and 2008-09-01 there are 1 years, 0 months, and 5 days. */  class Extended_DateTime extends DateTime {      public function find_TimeFromThisTo($newer) {         $timefrom = array('years'=>0,'months'=>0,'days'=>0);          // Clone because we're using modify(), which will destroy the object that was passed in by reference         $testnewer = clone $newer;          $timefrom['years'] = $this->find_YearsFromThisTo($testnewer);         $mod = '-'.$timefrom['years'].' years';         $testnewer -> modify($mod);          $timefrom['months'] = $this->find_MonthsFromThisTo($testnewer);         $mod = '-'.$timefrom['months'].' months';         $testnewer -> modify($mod);          $timefrom['days'] = $this->find_AllDaysFromThisTo($testnewer);         return $timefrom;     } // end function find_TimeFromThisTo       public function find_YearsFromThisTo($newer) {         /*         If the passed is:         not an object, not of class DateTime or one of its children,         or not larger (after) $this         return false         */         if (!is_object($newer) || !($newer instanceof DateTime) || $newer->format('U') < $this->format('U'))             return FALSE;         $count = 0;          // Clone because we're using modify(), which will destroy the object that was passed in by reference         $testnewer = clone $newer;          $testnewer -> modify ('-1 year');         while ( $this->format('U') < $testnewer->format('U')) {             $count ++;             $testnewer -> modify ('-1 year');         }         return $count;     } // end function find_YearsFromThisTo       public function find_MonthsFromThisTo($newer) {         /*         If the passed is:         not an object, not of class DateTime or one of its children,         or not larger (after) $this         return false         */         if (!is_object($newer) || !($newer instanceof DateTime) || $newer->format('U') < $this->format('U'))             return FALSE;          $count = 0;         // Clone because we're using modify(), which will destroy the object that was passed in by reference         $testnewer = clone $newer;         $testnewer -> modify ('-1 month');          while ( $this->format('U') < $testnewer->format('U')) {             $count ++;             $testnewer -> modify ('-1 month');         }         return $count;     } // end function find_MonthsFromThisTo       public function find_AllDaysFromThisTo($newer) {         /*         If the passed is:         not an object, not of class DateTime or one of its children,         or not larger (after) $this         return false         */         if (!is_object($newer) || !($newer instanceof DateTime) || $newer->format('U') < $this->format('U'))             return FALSE;          $count = 0;         // Clone because we're using modify(), which will destroy the object that was passed in by reference         $testnewer = clone $newer;         $testnewer -> modify ('-1 day');          while ( $this->format('U') < $testnewer->format('U')) {             $count ++;             $testnewer -> modify ('-1 day');         }         return $count;     } // end function find_AllDaysFromThisTo       public function find_WeekdaysFromThisTo($newer) {         /*         If the passed is:         not an object, not of class DateTime or one of its children,         or not larger (after) $this         return false         */         if (!is_object($newer) || !($newer instanceof DateTime) || $newer->format('U') < $this->format('U'))             return FALSE;          $count = 0;          // Clone because we're using modify(), which will destroy the object that was passed in by reference         $testnewer = clone $newer;         $testnewer -> modify ('-1 day');          while ( $this->format('U') < $testnewer->format('U')) {             // If the calculated day is not Sunday or Saturday, count this day             if ($testnewer->format('w') != '0' && $testnewer->format('w') != '6')                 $count ++;             $testnewer -> modify ('-1 day');         }         return $count;     } // end function find_WeekdaysFromThisTo      public function set_Day($newday) {         if (is_int($newday) && $newday > 0 && $newday < 32 && checkdate($this->format('m'),$newday,$this->format('Y')))             $this->setDate($this->format('Y'),$this->format('m'),$newday);     } // end function set_Day       public function set_Month($newmonth) {         if (is_int($newmonth) && $newmonth > 0 && $newmonth < 13)             $this->setDate($this->format('Y'),$newmonth,$this->format('d'));     } // end function set_Month       public function set_Year($newyear) {         if (is_int($newyear) && $newyear > 0)             $this->setDate($newyear,$this->format('m'),$this->format('d'));     } // end function set_Year } // end class Extended_DateTime