PHP实现折半查询算法

PHP实现折半查询算法，自己写代码，可能不规范。

什么是折半查询算法？具体文字描述自己百度。直接上代码：

<?php
header("Content-type: text/html; charset=utf-8");

/* 折半查询算法--不用递归 */
function qSort($data = array(), $x = 0){
$startIndex = 0; // 开始索引
$endIndex = count($data) - 1; // 结束索引
$index = 0;
$number = 0; // 计数器
do{
if($endIndex > $startIndex){
$searchIndex = ceil(($endIndex - $startIndex) / 2);
}else if($endIndex == $startIndex){
$searchIndex = $endIndex;
}else{
$index = -1;
break;
}
$searchIndex += ($startIndex - 1);

echo '检索范围：'.$startIndex.' ~ '.$endIndex.'<br>检索位置：'.$searchIndex.'检索值为：'.$data[$searchIndex];
echo '<br>=======================<br><br>';

if($data[$searchIndex] == $x){
$index = $searchIndex;
break;
}else if($x > $data[$searchIndex]){
$startIndex = $searchIndex + 1;
}else{
$endIndex = $searchIndex - 1;
}

$number++;
}while($number < count($data));
return $index;
}

/* 折半查询算法--使用递归 */
function sSort($data, $x, $startIndex, $endIndex){
if($endIndex > $startIndex){
$searchIndex = ceil(($endIndex - $startIndex) / 2);
}else if($endIndex == $startIndex){
$searchIndex = $endIndex;
}else{
return -1;
}

$searchIndex += ($startIndex - 1);

echo '检索范围：'.$startIndex.' ~ '.$endIndex.'<br>检索位置：'.$searchIndex.'检索值为：'.$data[$searchIndex];
echo '<br>=======================<br><br>';

if($data[$searchIndex] == $x){
return $searchIndex;
}else if($x > $data[$searchIndex]){
$startIndex = $searchIndex + 1;
return sSort($data, $x, $startIndex, $endIndex);
}else{
$endIndex = $searchIndex - 1;
return sSort($data, $x, $startIndex, $endIndex);
}
}

$data = array(1, 3, 4, 6, 9, 11, 12, 13, 15, 20, 21, 25, 33, 34, 35, 39, 41, 44);

$index = qSort($data, 11); // 不用递归的排序方法
$index = sSort($data, 11, 0, count($data) - 1); // 使用递归的排序方法
echo '结果：'.$index;