找出数组中的最大值及其索引

<?php

$arr = [11,18,21,141,811];
$max = $arr[0];
$max_key = 0;
foreach( $arr as $key => $value)
{
  if($value > $max)
  {
    $max = $value;//哪个最大就赋值给$max
    $max_key = $key;//最大值,索引赋值
  }

}
echo $max,'索引是:'.$max_key;