How to get the date of Easter in PHP?

If PHP is compiled with --enable-calendar, you can use easter_date(): http://php.net/manual/en/function.easter-date.php

if (time() <= easter_date(2017)) {
    echo 'HaPHPy Easter!';
}

and easter_days(): http://php.net/manual/en/function.easter-days.php

The computation of the date of Easter can also be done manually.