问如何格式化时间戳以只显示没有时间的日期

EN

if (php_sapi_name() == 'apache') {
    // if our web server is apache
    // we get check HTTP
    // If-Modified-Since header
    // and do not send image
    // if there is a cached version

    $ar = apache_request_headers();
    if (isset($ar['If-Modified-Since']) && // If-Modified-Since should exists
        ($ar['If-Modified-Since'] != '') && // not empty
        (strtotime($ar['If-Modified-Since']) >= $image_time)) // and grater than
        $send_304 = true;                                     // image_time
}


if ($send_304)
{
    // Sending 304 response to browser
    // "Browser, your cached version of image is OK
    // we're not sending anything new to you"
    header('Last-Modified: '.gmdate('D, d M Y H:i:s', $ts).' GMT', true, 304);

    exit(); // bye-bye
}

// outputing Last-Modified header
header('Last-Modified: '.gmdate('D, d M Y H:i:s', $image_time).' GMT',
        true, 200);

// Set expiration time +1 year
// We do not have any photo re-uploading
// so, browser may cache this photo for quite a long time
header('Expires: '.gmdate('D, d M Y H:i:s',  $image_time + 86400*365).' GMT',
        true, 200);