在用户使用PHP输入日期后获取3年的日期

I have a date input as <input type="date" name="date_register" id="date_register" value="date" /> I want to print the date after 3 years of the user entered date. How can i get using PHP?

Try this :

<?php
    $date = isset($_REQUEST['date_register']) ? $_REQUEST['date_register'] : date('Y/m/d');

    $three_yrs = date('Y/m/d', strtotime($date .' +3 years'));
    Echo $three_yrs;
?>

Check out the PHP DateTime class. Here is an example that should help you get started:

$date = new DateTime($_POST['date_register'];
$date->modify('+3 years');

var_dump($date);
echo $date->format('F j, Y');

 //i assume that your field name is date_register and method used is post
 $unix_date_after_add_3_years = strtotime($_POST["date_register"]." +3 years",);
 //now formatting the result to be for example 17-9-2014 using function date
 echo date("Y-m-d",$unix_date_after_add_3_years);