PHP统计一个数字在排序数组中出现的次数

<?php
function GetNumberOfK($data, $k)
{
  if(count($data)==0){
    return 0;
  }
  $index = 0;
  $low = 0;
  $high = count($data)-1;
  $middle = 0;
  //二分查找找到k的index
  while($low<=$high){
    $middle = ($high+$low)>>1;
    if($data[$middle]==$k){
      $index = $middle;
      break;
    }
    else if($data[$middle]>$k) {
      $high = $middle -1;
    }else{
      $low = $middle+1;
    }
    $index = -1;
  }
  // console.log(index);
  // 如果没找到
  if($index==-1){
    return 0;
  }
  //找到了 分别往左右查找边界
  $start = $index;
  $end = $index;
  $count = 0;
  while($data[$start]==$k){
    $count++;
    $start--;
  }
  while($data[$end]==$k){
    $count++;
    $end++;
  }
  return $count-1;
}