Lazy deterministic RNG for games

rng.php

<?php

class ProceduralNumericSequenceGenerator {
    private $algo, $state;
    
    public function __construct($seed = NULL, $algo = "sha256") {
        if ($seed === NULL) {
            $seed = time();
        }
        
        if (array_search($algo, hash_algos()) === FALSE) {
            throw new RuntimeException("Hashing algorithm \"$algo\" is not available.");
        }
        
        $this->state = $seed;
        $this->algo = $algo;
    }
    
    public function getInt() {
        return hexdec(substr($this->state, 0, PHP_INT_SIZE));
    }
    
    public function advance() {
        $this->state = hash($this->algo, $this->state);
    }
    
    public function advanceNew() {
        $new = clone $this;
        $new->advance();
        return $new;
    }
    
    public function advanceAndGetInt() {
        $this->advance();
        return $this->getInt();
    }
    
    public function advanceNewAndGetInt() {
        $new = $this->advanceNew();
        return [$new->getInt(), $new];
    }
}