Page 525 - Beginning PHP 5.3

Chapter 16: PHP and the Outside World
Next comes checkDateOfBirth(), the callback function to check that the entered date is valid. As you
might expect, this uses PHP’s checkdate() function to do the checking. Because the element to be
checked contains multiple field values, HTML_QuickForm provides an associative array of the values,
keyed by field name. checkDateOfBirth() extracts these three values and passes them to
checkdate() for checking, passing checkdate()’s return value (true or false) back to the
calling code:

function checkDateOfBirth( $value ) {
return checkdate( $value[“M”], $value[“d”], $value[“Y”] );
}

The last function, calculateDays(), is called when the form is processed. First it creates two
timestamps: $currentDate, which stores the current date and time; and $dateOfBirth, which stores
the entered birth date. Both timestamps are created using mktime(). The month, day, and year
components of the date of birth are extracted from the three-element associative array stored in the
form’s dateOfBirth field:

$currentDate = mktime();
$dateOfBirth = mktime( 0, 0, 0, $values[“dateOfBirth”][“M”],
$values[“dateOfBirth”][“d”], $values[“dateOfBirth”][“Y”] );
Now that both dates are stored in timestamps, it’s easy to work out the number of seconds between the
two, and hence the number of days:

$secondsOld = $currentDate - $dateOfBirth;
$daysOld = (int) ( $secondsOld / 60 / 60 / 24 );
Finally, the function displays the output to the visitor. First it calls PHP’s date() function to display the
visitor’s date of birth in a nice format, then it tells the visitor how old he is in days:

echo “<p>You were born on “ . date( “l, F jS, Y”, $dateOfBirth ) . “.</p>”;
echo “<p>You are “ . number_format( $daysOld ) . “ day” . ( $daysOld != 1 ?
“s” : “” ) . “ old!</p>”;
Calculating the difference in days by dividing the difference in seconds by (60 * 60 * 24) is not entirely
accurate due to days not always being 24 hours long (at least in time zones that use daylight saving
time). However, it’s good enough for the purposes of this script.

DateTime: The Future of PHP Date/Time Handling

Starting with version 5.2, PHP introduced a couple of useful date and time handling classes:
❑ DateTime for storing and manipulating dates and times
❑ DateTimeZone for representing time zones

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