/**
* Determines whether all letters in the specified word can be
* formed from the letters available in the sentence.
*
* Rules:
* - Letter order does not matter.
* - Comparison is case-insensitive.
* - Non-alphabetic characters are ignored.
*
* @param string $sentence Source text containing available letters.
* @param string $word Word to check.
*
* @return bool True if the word can be formed; otherwise false.
*/
function containsWordLetters(string $sentence, string $word): bool
{
$available = array_fill(0, 26, 0);
// Count available letters in the sentence.
foreach (str_split(strtolower($sentence)) as $char) {
if ($char >= 'a' && $char <= 'z') {
$available[ord($char) - ord('a')]++;
}
}
// Consume letters required by the word.
foreach (str_split(strtolower($word)) as $char) {
if ($char < 'a' || $char > 'z') {
continue;
}
$index = ord($char) - ord('a');
if (--$available[$index] < 0) {
return false;
}
}
return true;
}
// Example usage.
$sentence = 'Bright stars shine above calm valleys at night.';
$word = 'satellite';
var_dump(containsWordLetters($sentence, $word));
$word = 'satellllite'; // Requires 5 occurrences of 'l'
var_dump(containsWordLetters($sentence, $word));
/*
run:
bool(true)
bool(false)
*/
