怎么用php将时间戳转换为星期几

$timestamp = time();
$weekday = date("l", $timestamp);
echo "Today is ".$weekday; //输出"Today is Friday"

$timestamp = time();
$weekday = date("D", $timestamp);
echo "Today is ".$weekday; //输出"Today is Fri"

$timestamp = time();
$weekday_number = date("w", $timestamp);
echo "Today is ".$weekday_number; //输出"Today is 5"

$timestamp = time();
$weekday_number = date("w", $timestamp);
$weekdays = array("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday");
echo "Today is ".$weekdays[$weekday_number]; //输出"Today is Friday"

$timestamp = time();
$weekday_number = date("w", $timestamp);
switch ($weekday_number) {
case 0:
    $weekday = "Sunday";
    break;
case 1:
    $weekday = "Monday";
    break;
case 2:
    $weekday = "Tuesday";
    break;
case 3:
    $weekday = "Wednesday";
    break;
case 4:
    $weekday = "Thursday";
    break;
case 5:
    $weekday = "Friday";
    break;
case 6:
    $weekday = "Saturday";
    break;
}
echo "Today is ".$weekday; //输出"Today is Friday"