How to get the day of the week for a specified date in PHP

<?php
  header("Content-type: text/html; charset=utf-8");
  //获取星期方法
  function get_week($date){
    //强制转换日期格式
    $date_str=date(&#39;Y-m-d&#39;,strtotime($date));
    //封装成数组
    $arr=explode("-", $date_str);
    //参数赋值
    //年
    $year=$arr[0];
    //月，输出2位整型，不够2位右对齐
    $month=sprintf(&#39;%02d&#39;,$arr[1]);
    //日，输出2位整型，不够2位右对齐
    $day=sprintf(&#39;%02d&#39;,$arr[2]);
    //时分秒默认赋值为0；
    $hour = $minute = $second = 0;
    //转换成时间戳
    $strap = mktime($hour,$minute,$second,$month,$day,$year);
    //获取数字型星期几
    $number_wk=date("w",$strap);
    //自定义星期数组
    $weekArr=array("星期日","星期一","星期二","星期三","星期四","星期五","星期六");
    //获取数字对应的星期
    return $weekArr[$number_wk];
  }
  //测试
  $date="2016-08-20";
  echo get_week($date);
  //星期六
?>