count-words.php

<?php

$dir = '/Users/flaviosilveira/Dropbox/php-mentors/manuscript';
$result = array();

foreach(scandir($dir) as $file){

	switch ($file){
		case '.':
		case '..':
		case 'Book.txt':
		case 'before_start.txt':
		case 'disclaimer.txt':
		case 'images':
		case 'introduction.txt':
		case 'profiles.txt':
		case 'questions.txt':
		case 'some_last_words.txt':
		case 'what_are_they_talking_about.txt':
			continue 2;
		break;

		default:
			$stringArr = file($dir . '/'  . $file);
			$fileString = '';
			foreach($stringArr as $string){
				if(strpos($string, '---') === 0){
					continue;
				}

				if(strpos($string, '**') === 0){
				} else {
					$fileString .= ' ' . $string  . ' ';
				}
			}

			$words = preg_split('/[\s]+/', $fileString, -1, PREG_SPLIT_NO_EMPTY);
			$wordInFile = array();

			foreach($words as $word){
				$word = preg_replace("/[^a-zA-Z]/", "", $word);
				$word = strtolower($word);
				
				if(!in_array($word, $wordInFile)){
					if(array_key_exists($word,$result)){
						$result[$word] = $result[$word]+1;
					} else {
						$result[$word] = 1;
					}
				}
				$wordInFile[] = $word;
			}
	}
}
arsort($result);
print_r($result);