Weighted Randomised Selection

<?php
class MarkovGenerator
{
    protected $dictionary = [];
    protected $totals = [];
    public function loadText($text)
    {
        // ...
        foreach ($this->dictionary as $sequence => $values) {
            $this->totals[$sequence] = array_sum($values);
        }
    }
    protected function getWord($seed)
    {
        $rand = rand(1, $this->totals[$seed]);
        foreach ($this->dictionary[$seed] as $word => $count) {
            $rand -= $count;
            if ($rand <= 0) {
                return $word;
            }
        }
        return null;
    }
    public function generateText($seed = null, $length = 100)
    {
        if ($seed == null) {
            $seed = array_rand($this->dictionary);
        }
        // Set the output to the initial seed word.
        $output = $seed;
        for ($i = 0; $i < $length; $i++) {
            // Stop generating if the word does
            // not exist inside our dictionary.
            if (! array_key_exists($seed, $this->dictionary)) {
                break;
            }
            $nextWord = array_rand($this->dictionary[$seed]);
            $nextWord = $this->getWord($seed);
            if ($nextWord == null) {
                break;
            }
            $output .= ' ' . $nextWord;
            // Reset the seed to continue our generation.
            $seed = $nextWord;
        }
        return $output;
    }
}