<?php
if (!function_exists('calculate_age')) {
	// Checked this function against http://www.timeanddate.com/date/duration.html

	function calculate_age($startdate = '0000-00-00', $enddate = '0000-00-00') {
		
		// Check to see if start date is valid

		@list($year, $month, $day) = explode('-', $startdate);
		if (@!checkdate($month,$day,$year)) {
			return false;
		}
		
		// Create a new datetime object to do our calculations with
		$s = new DateTime($startdate);
		// We have to have an end date so if it is empty or 0000-00-00 we will make it right now
		if (empty($enddate) OR $enddate == '0000-00-00') {
			$enddate = 'now';
		} else {
			// Check to see if end date is valid

			@list($year, $month, $day) = explode('-', $enddate);
			if (@!checkdate($month,$day,$year)) {
				return false;
			}
		}
		// Create a new datetime object to compare as an end date
		$e = new DateTime($enddate);
		
		if ($s->format('Ymd') > $e->format('Ymd')) {
			// End date cannot be before start date
			return false;
		}
		
		// Calculate our base numbers here
		$years = $e->format('Y')-$s->format('Y');
		$months = $e->format('m')-$s->format('m');
		$days = $e->format('d')-$s->format('d');

		// We cannot have negative days
		// Calculate how many days are in the startdate month
		// subtract the startdate day and add 1
		// Then add back in the day of the enddate
		// Subtract 1 month
		if ($days < 0) {
			$days = $s->format('t')-$s->format('d')+1;
			$days += $e->format('d');
			$months--;
		}
		
		// We cannot have negative months
		// Subtract 1 year and add back 12 months to make months positive
		if ($months < 0) {
			$years--;
			$months += 12;
		}

		return array('years'=>$years,'months'=>$months, 'days'=>$days);
	}
}
?>

<?php
// Current date is 2010-01-19
$birthday = '1986-09-23';
$age = calculate_age($birthday);
var_dump($age);
echo '<hr />';
$startdate = '1985-09-06';
$enddate = '1986-09-23';
$difference = calculate_age($startdate, $enddate);
var_dump($difference);
?>

<?php
function GetDayByPosition($Position, $Weekday, $Month, $Year) {
	// Sanatize some of the inputs
	$Position = strtolower($Position);
	$Weekday = strtolower($Weekday);
	
	// Go to next month so we can then go back 1 week at end of script for calculating last xxx of month
	if ($Position=='last') { $Month += 1; }
        // We cannot have 13 months so set as January of the next year.
	// This was pointed out by Evan who made a comment on the posting of this script
	if ($Month > 12) {
		$Month = 1;
		$Year += 1;
	}
	// Create new date object for the first of the month
	$D = new DateTime($Year.'-'.$Month.'-1');
	$DOW = $D->format('w'); // Get the current day of the week based on the 1st of the month
	$keys = array('sunday'=>0,'monday'=>1,'tuesday'=>2,'wednesday'=>3,
				  'thursday'=>4,'friday'=>5,'saturday'=>6);
	// Calculate what the offset is based on the current day of the week
	// vs the day in the week you want to get
	$offset = $keys[$Weekday] - $DOW;
	if ($offset<0) { $offset += 7; }

	switch ($Position) {
		// Don't need to add anything to first
		case 'second':
			$offset += 7; // Add 1 week
			break;
		case 'third':
			$offset += 14; // Add 2 weeks
			break;
		case 'fourth':
			$offset += 21; // Add 3 weeks
			break;
		case 'last':
			$offset -= 7; // Go back 7 days
			break;
	}
	// Add the current offset of days to the date object
	$D->modify('+'.$offset.' days');
	return $D->format('Y-m-d');
	
}
?>

<?php
// This will output 2009-01-05
echo 'First Monday of January 2009: ',GetDayByPosition('first', 'monday', 1, 2009),'<br />';
// This will output 2009-01-13
echo 'Second Tuesday of January 2009: ',GetDayByPosition('second', 'tuesday', 1, 2009),'<br />';
// This will output 2009-01-21
echo 'Third Wednesday of January 2009: ',GetDayByPosition('third', 'wednesday', 1, 2009),'<br />';
// This will output 2009-01-22
echo 'Fourth Thursday of January 2009: ',GetDayByPosition('fourth', 'thursday', 1, 2009),'<br />';
// This will output 2009-01-30
echo 'Last Friday of January 2009: ',GetDayByPosition('last', 'friday', 1, 2009),'<br />';
?>

<?php

function MyDateCheck($Date, $ReturnFormat = 'm/d/Y') {
	// Clean date to make sure it has legal characters
	$Date = preg_replace("/[^0-9._\/\\\-]/", '', $Date);
	
	if (empty($Date) OR empty($ReturnFormat)) {
		// We do not have everything that we need to complete the function, return false
		return false;
	}
	// Replace a variety of date separators with one common separator
	$Date = str_replace(array('_', '.', '\', '-'), '/', $Date);
	// Start the date checking
	//Matches mm/dd/yy, mm/dd/yyyy and only allows days from 1 to 31
	if (preg_match("/^([0-1][0-2]|[0]?[0-9])\/([0-2][0-9]|3[01]|[0-9])\/([0-9]{2,4})$/", $Date, $parts)) {
		// Using the $parts array parse out the month, day and year for further date calculations
		// We convert them into Integers so there is no possible way of any stray characters missed from the replace above
		$Month = (INT) $parts[1];
		$Day = (INT) $parts[2];
		$Year = (INT) $parts[3];
	// Matches yyyy/mm/dd and only allows days from 1 to 31
	} elseif (preg_match("/^([0-9]{4})\/([0-1][0-2]|[0]?[0-9])\/([0-2][0-9]|3[01]|[0-9])$/", $Date, $parts)) {
		$Year = (INT) $parts[1];
		$Month = (INT) $parts[2];
		$Day = (INT) $parts[3];
	} else {
		return false;
	}
	// If the date gets past the matching we confirm the date with checkdate
	// This function also works to detect any bad dates due to leap year
	if (checkdate($Month, $Day, $Year)) {
		// Using PHP5's DateTime object to format the date
		$NewDate = new DateTime($Date);
		// Return date in a new format, defaulted to m/d/Y
		return $NewDate->format($ReturnFormat);
	}
	// Return false by default if something happens above that is not expected
	return false;
}

?>

<?php
$Date = '10-16-2008';
if ($MyDate = MyDateCheck($Date)) {
       // Use your value from $MyDate as it is now safe and in correct format
	echo 'A correct date was passed through: '.$MyDate.'<br />';
} else {
	echo $Date.' is not a valid date';
}
?>

<?php
$Date = '10-16-2008';
if ($MyDate = MyDateCheck($Date, 'mm-dd-yy')) {
       // Use your value from $MyDate as it is now safe and in correct format
	echo 'A correct date was passed through: '.$MyDate.'<br />';
} else {
	echo $Date.' is not a valid date';
}
?>

<?php
function getMondays($year) {
  $newyear = $year;
  $week = 0;
  $day = 0;
  $mo = 1;
  $mondays = array();
  $i = 1;
  while ($week != 1) {
   $day++;
   $week = date("w", mktime(0, 0, 0, $mo,$day, $year));
  }
  array_push($mondays,date("r", mktime(0, 0, 0, $mo,$day, $year)));
  while ($newyear == $year) {
   $test =  strtotime(date("r", mktime(0, 0, 0, $mo,$day, $year)) . "+" . $i . " week");
   $i++;
   if ($year == date("Y",$test)) {
     array_push($mondays,date("r", $test));
   }
   $newyear = date("Y",$test);
  }
  return $mondays;
}
echo '<pre>';
print_r(getMondays('2006'));
echo '</pre>';
?>

<?php
function timeLeft($theTime) {
  $now = strtotime("now");
  $timeLeft = $theTime - $now;
  
  if($timeLeft > 0) {
    $days = floor($timeLeft/60/60/24);
    $hours = $timeLeft/60/60%24;
    $mins = $timeLeft/60%60;
    $secs = $timeLeft%60;
    
    if($days) {
      $theText = $days . " Day(s)";
      if($hours) {
        $theText .= ", " .$hours . " Hour(s) ";
      }
    } elseif($hours) {
      $theText = $hours . " Hour(s)";
      if($mins) {
        $theText .= ", " .$mins . " Minute(s) ";
      }
    } elseif($mins) {
      $theText = $mins . " Minute(s)";
      if($secs) {
        $theText .= ", " .$secs . " Second(s) ";
      }
    } elseif($secs) {
      $theText = $secs . " Second(s)";
    }
  } else {
    $theText = "The countdown is over!";
  }

  return $theText;
}
?>

<?php
$testTime = strtotime("next Friday");
echo timeLeft($testTime).'<br>';

$testTime = strtotime("+1 year 1 month 1 week 1 days 1 hours 1 seconds");
echo timeLeft($testTime).'<br>';

$testTime = mktime(0, 0, 0, date("m")+1, date("d"), date("y"));
echo timeLeft($testTime);
?>

<?php
$lowEnd=date("w");
$lowEnd=-$lowEnd;
$highEnd=$lowEnd + 6;
$weekday=0; // Change this to make the Sunday index 1
for($i=$lowEnd; $i<=$highEnd; $i++) {
  $WeekDate[$weekday]=date("m/d",mktime(0, 0, 0, date("m")  , date("d")+$i, date("Y")));
  $weekday++;
}
echo '<pre>';
print_r($WeekDate);
echo '</pre>';
?>

Array
(
    [0] => 07/30
    [1] => 07/31
    [2] => 08/01
    [3] => 08/02
    [4] => 08/03
    [5] => 08/04
    [6] => 08/05
)