time() and date() give you ways to work with the current time and date. mktime() gives you a way to work with almost any time and dates from 1970 to 2038 if your server is before PHP 5.1.0. After PHP 5.1.0, the valid range is from 1901 to 2038
mktime() returns a timestamp and has six optional arguments: hour, minute, second, month, day of month and year. Arguments may be left out in order from right to left; any arguments left out will be set to the current time and/or date. For example, if you want to find out what day of the week Christmas falls on in 2020, you can use mktime() to get a time stamp for 6:00 AM, 12/25/2005, use getdate() to convert the timestamp into an array then use the key, weekday to get the day of the week:
<?
$xmas = mktime(6,0,0,12,25,2020);
$xmas = getdate($xmas);
echo "Christmas 2020 falls on $xmas[weekday]";
?>
Christmas 2020 falls on Friday
strtotime() is a function that can convert a string of English words into a timestamp. For example, to get a timestamp for next friday, all you have to do is use strtotime("next friday"), assign it to a variable, use date() to format it into a string and echo it:
<?
$next_friday = strtotime("next friday");
$next_friday = date("F jS Y", $next_friday);
echo "Next friday falls on $next_friday";
?>
Next friday falls on February 10th 2012
| Words and abbreviations recognized by strtotime() | Month names | Full name or abbreviations |
|---|---|
| Days of the week | Full name or abbreviations |
| Time units | Year, month, fortnight, week, day, hour, minute, second, am, pm |
| Plus or minus | + or - |
| All numbers | |
| Time zone | gmt, pdt, akst etc. |
checkdate() is used to validate dates. It accepts three integers as arguments; month, day and year and returns true if the numbers represent a valid date between the year 0 and 32767 and false if it is not. If letters are used as an argument, checkdate() will generate a PHP error message. You can suppress that error message by appending a @ to checkdate().
Below is an example of a form using checkdate() to validate the input.
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