code to display a select of year based on the current year

select_year.php

/** source: http://stackoverflow.com/a/18608587/1252947 **/
<?php
  <select id="year">
    <?
    $currentValue = date("Y");
    $past = 20;
    $future = 0;
    if ($currentValue && ($currentValue < date('Y') - $past || $currentValue > date('Y') + $future)) {
      echo "<option value=\"$currentValue\" selected=\"selected\">$currentValue</option>\n";
    }
    for ($year = date('Y') - $past; $year <= date('Y') + $future; $year++) {
      if ($year == $currentValue) {
        echo "<option value=\"$year\" selected=\"selected\">$year</option>\n";
      } else {
        echo "<option value=\"$year\">$year</option>\n";
      }
    }
    ?>
  </select>