PHP Cookbook

3.8. Validating a Date

Problem

You want to check if a date is valid. For example, you want to make sure a user hasn’t provided a birthdate such as February 30, 1962.

Solution

Use checkdate( ):

$valid = checkdate($month,$day,$year);

Discussion

The function checkdate( ) returns true if $month is between 1 and 12, $year is between 1 and 32767, and $day is between 1 and the correct maximum number of days for $month and $year. Leap years are correctly handled by checkdate( ), and dates are rendered using the Gregorian calendar.

Because checkdate( ) has such a broad range of valid years, you should do additional validation on user input if, for example, you’re expecting a valid birthdate. The Guinness Book of World Records says the oldest person ever reached 122. To check that a birthdate indicates a user between 18 and 122 years old, use the pc_checkbirthdate( ) function shown in Example 3-1.

Example 3-1. pc_checkbirthdate( )

function pc_checkbirthdate($month,$day,$year) { $min_age = 18; $max_age = 122; if (! checkdate($month,$day,$year)) { return false; } list($this_year,$this_month,$this_day) = explode(',',date('Y,m,d')); $min_year = $this_year - $max_age; $max_year = $this_year - $min_age; print "$min_year,$max_year,$month,$day,$year\n"; if (($year > $min_year) && ($year < $max_year)) { return true; } elseif (($year == $max_year) && (($month < $this_month) || (($month == $this_month) && ($day <= $this_day)))) { return true; } elseif (($year == $min_year) && (($month > $this_month) ...