simple HTML strip toy

<?php


class StripHtmlFsm {

    private $state;
    private $empty = false;
    private $HTML;
    private $output = '';

    public function __construct($HTML) {
        $this->HTML = $HTML;
        $this->state = 'text';
    }

    public function parse_transform() {
        $STOPPER = 100;
        while (!$this->empty) {
            $this->{$this->state}();
        }
    }

    public function output() {
        return $this->output;
    }

    ## -----------------------------------------------
    ## parse/buffer tools
    ## -----------------------------------------------

    private function lookup($start_chars) {
        $len = strlen($start_chars);
        $extr = substr($this->HTML, 0, $len);
        echo "lookup '$extr'\n";
        if ($extr == $start_chars) {
            return true;
        }
        return false;
    }

    private function bufferize($str) {
        $this->output .= $str;
    }

    private function check_empty() {
        if (strlen($this->HTML) < 1) {
            echo "HTML is empty\n ";
            $this->empty = true;
        }

    }

    private function move($amount) {
        echo 'moving \'' . substr($this->HTML, 0, $amount) . "'\n";
        $this->bufferize(substr($this->HTML, 0, $amount));
        $this->HTML = substr($this->HTML, $amount);
        $this->check_empty();
    }

    private function delete($amount) {
        echo 'delete \'' . substr($this->HTML, 0, $amount) . "'\n";
        $this->HTML  = substr($this->HTML, $amount);
        $this->check_empty();
    }

    ## -----------------------------------------------
    ## Etats de la FSM
    ## -----------------------------------------------

    private function change_state($state) {
        $transition = "{$this->state}_to_$state";
        echo "Transition $transition\n";
        $this->{$transition}();
        echo "New state $state\n";
        $this->state = $state;
    }

    private function text() {
        if ($this->lookup('<')) {
             $this->change_state('start_tag');
         }
        else {
            $this->move(1);
            /*echo "next\n";*/
        }
    }

    private function start_tag() {
        if ($this->lookup(' ')) {
            $this->change_state('attr_list');
        }
        elseif ($this->lookup('/>')) {
            $this->change_state('text');
        }
        elseif ($this->lookup('>')) {
            $this->change_state('text');
        }
        else {
             $this->delete(1);
        }
    }

    private function attr_list() {
        if ($this->lookup('="')) {
            $this->delete(2);
            $this->change_state('attr_val');
        }
        elseif ($this->lookup('/>')) {
            $this->change_state('text');
        }
        elseif ($this->lookup('>')) {
            $this->change_state('text');
        }
        else {
            $this->delete(1);
        }
    }

    private function attr_val() {
        if ($this->lookup('')) {

        }
        if ($this->lookup('\"')) {
            $this->delete(2);
        }
        elseif ($this->lookup('"')) {
            $this->delete(1);
            $this->change_state('attr_list');
        }
        else {
            $this->delete(1);
        }
    }

    ## -----------------------------------------------
    ## Transitions de la FSM
    ## -----------------------------------------------

    private function text_to_start_tag() {
        $this->delete(1);
    }

    private function start_tag_to_attr_list() {
    }

    private function attr_list_to_attr_val() {
    }

    private function attr_val_to_attr_list() {
    }

    private function attr_list_to_text() {
        $this->start_tag_to_text();
    }

    private function start_tag_to_text() {
        if ($this->lookup('/>')) {
            $this->delete(2);
        }
        else {
            $this->delete(1);
            $this->bufferize('_');
        }
    }



}
set_time_limit(3);
header('content-type: text/plain; charset=utf8');
ini_set('html_errors','off');
$HTML = 'hallo mon nom est <strong class="qzd\">mou">Jeorg</strong>,<br/> et toi ?';
$p = new StripHtmlFsm($HTML);
$p->parse_transform();
var_dump($p);
echo $p->output();