Determine if the first letter of a string is uppercase and is A-Z

StringHelpers.php

<?php
/**
 * Determine if the first letter of a string is uppercase and is A-Z
 *
 * Note: we use ctype here as it uses the current locale to help with multi-language/emoji decoding.
 *
 * @param string $string
 * @return bool
 */
function isFirstLetterUppercase(string $string): bool
{
    // Grab our first letter
    $firstLetter = substr($string, 0, 1);

    // True when both uppercase and A-Z passes
    return ctype_upper($firstLetter) && ctype_alpha($firstLetter);
}