return the max words of sentences, which is from a text

max-words-of-sentences.php

<?php

/**
 * return the max words of sentences, which is from a text
 *
 * @param $s
 * @return mixed
 * @author Phan Vu Hoang <vu-hoang.phan@ekino.com>
 */
function solution($s)
{
    $delimiters      = ['.', '?', '!'];
    $ready           = str_replace($delimiters, $delimiters[0], $s);
    $launch          = explode($delimiters[0], $ready);
    $arr_words_count = [];
    foreach ($launch as $index => $sen) {
        $ps          = explode(" ", $sen);
        $non_letters = [];
        foreach ($ps as $p) {
            if (is_numeric($p) || $p === '') {
                $non_letters[] = $p;
            }
        }
        $letters           = array_diff($ps, $non_letters);
        $arr_words_count[] = count($letters);
    }
    
    return max($arr_words_count);
}