Simple binary search [algorithm]

binary_search.php

<?php

$input = [
    1,
    3,
    5,
    2,
    4,
    6,
    8,
    7
];

// sort the array
sort($input);


/**
 * Search value
 *
 * @param integer $search
 * @param array $input
 * @return integer|boolean
 */
function searchValue($search, $input)
{
    $leftBorder  = 0;
    $rightBorder = count($input) - 1;

    while (true) {
        $middle =  floor(($leftBorder + $rightBorder) / 2);

        // go down
        if ($search > $input[$middle]) {
            $leftBorder = $middle + 1;
        }
        else if ($search < $input[$middle]) {
            // go up
            $rightBorder = $middle - 1;
        }
        else {
            // we've found the value
            return $input[$middle];
        }

        if ($leftBorder > $rightBorder || $rightBorder < $leftBorder) {
            return false;
        }
    }
}

var_dump( searchValue(5, $input) );