Sourceability

<?php

function isPalindrome(string $word): bool
{
    $hashMap = [];

    for ($i = 0; $i < strlen($word); $i++) {
        if (isset($hashMap[$word{$i}])) {
            $hashMap[$word{$i}] = $hashMap[$word{$i}] + 1;
        } else {
            $hashMap[$word{$i}] = 1;
        }
    }

    $odds = 0;

    foreach ($hashMap as $char) {
        if ($char % 2 !== 0 ) {
            $odds++;

            if ($odds > 1) {
                return false;
            }
        }
    }

    return true;
}

$words = [
    'bob',
    'a',
    'aa',
    'aaa',
    'aba',
    'abba',
    'abcba',
    'racceccar',
    'aab',
    'aabb',
    'acbba',
    'acccbbb',
];




foreach ($words as $word) {
    $result = isPalindrome($word);
    $val = ($result === true) ? 'true' : 'false';
    echo ($word . ' is ' . $val . "\n");
}