<?php

class Perceptron {

    protected $learnRate;
    protected $synapseWeight = array();
    protected $biaWeight;

    public static function factory($learnRate = 0.6) {
        return new static($learnRate);
    }

    public function __construct($learnRate = 0.6) {
        $this->learnRate = $learnRate;
    }

    protected function learnFunction($oldWeight, $errorValue, $value) {
        return $oldWeight + ($errorValue * $value * $this->learnRate);
    }

    protected function setSynapseWeight($synapse, $weight) {
        $this->synapseWeight[$synapse] = $weight;
    }

    protected function synapseWeight($synapse, $inicialize = 0) {
        if (!isset($this->synapseWeight[$synapse]))
            $this->synapseWeight[$synapse] = $inicialize;
        return $this->synapseWeight[$synapse];
    }

    public function process(Array $values) {
        $sum = 1 * $this->biaWeight;

        foreach ($values as $key => $value)
            $sum += $this->synapseWeight($key) * $value;

        return $sum > 0.5 ? 1 : 0;
    }

    public function forceLearn(Array $values, $learn) {
        while ($this->learn($values, $learn));
        return $this;
    }

    public function learn(Array $values, $learn) {
        if (($ret = $this->process($values)) == $learn)
            return false;

        $errorValue = $learn - $ret;

        $this->biaWeight = $this->
                learnFunction($this->biaWeight, $errorValue, 1);

        foreach ($values as $key => $value)
            $this->setSynapseWeight($key,
                    $this->learnFunction($this->synapseWeight($key),
                            $errorValue, $value));

        return true;
    }

}