Example of a simple function to perform a Binary Search in PHP to search for a String value

BinarySearchString.php

<?php

/**
 * @param string  $value    The value you're searching for
 * @param array   $dataSet  Your sorted data set to search
 *
 * @return int              Returns the key matched, or -1 if no match is found
 */
function binarySearchString(string $value, array $dataSet): int
{
    $start = 0;
    $end = count($dataSet) - 1;

    while ($start <= $end) {
        $middle = intdiv($end, 2);

        if ($value === $dataSet[$middle]) {
            return $middle;
        }

        if (strcmp($value, $dataSet[$middle]) < 0) {
            $end = $middle + 1;
            continue;
        }

        $start = $middle - 1;
    }

    return -1;
}