palindrome.php

<?php

class palindrome
{
    private static $caseSensitive = false;

    static function isPalindrome($word)
    {
        $reversedWord = strrev($word);
        if (!self::$caseSensitive) {
            $word = strtolower($word); // I assume we don't deal with unicode, if we do use mb_strtolower()
            $reversedWord = strtolower($reversedWord);
        }

        if ($word === $reversedWord) {
            return true;
        }

        return false;
    }

    static function setCaseSensitive()
    {
        self::$caseSensitive = true;
    }

    static function setCaseInsensitive()
    {
        self::$caseSensitive = false;
    }

}

var_dump('anna', palindrome::isPalindrome('anna'));
var_dump('annb', palindrome::isPalindrome('annb'));
var_dump('Anna', palindrome::isPalindrome('Anna'));
palindrome::setCaseSensitive();
var_dump('Anna', palindrome::isPalindrome('Anna'));
var_dump('civic', palindrome::isPalindrome('civic'));
var_dump('civia', palindrome::isPalindrome('aivic'));