$frequency = array();

    foreach($words[0] as $word) {

        unset($words[$word]);

        // This is the filter out the 'common words'
        if(in_array($word, $common_words)) continue;

        if(isset($frequency[$word])) {
            $frequency[$word] += 1;
        } else {
            $frequency[$word] = 1;
        }
    }

$total_words = array_count_values(str_word_count('your_string', 1));
print_r($total_words);