Binary Search

binary_search.php

<?php 

function binarySearch(array $searchArray, $needle)
{
    $length = count($searchArray);
    $centerKey = (int)($length / 2);
    $currentKey = $centerKey;
    $start = 0;
    $end = $length - 1;

    while (isset($searchArray[$currentKey])) {
        $center = $searchArray[$currentKey];
        if ($center === $needle) {
            return $currentKey;
        } elseif ($needle < $center) {
            $end = $currentKey - 1;
        } else {
            $start = $currentKey + 1;
        }

        $currentKey = (int)(($end - $start) / 2) + $start;
    };

    return false;
}