Leetify: "leet "-> "133+"; "133+" -> "leet"

Leetify.php

<?php
// The this code migrate to github project: https://github.com/romanitalian/Leetify

/**
 * Class Leetify
 * Leetify::encode('leet'); // "133+"
 * Leetify::decode('133+'); // "leet"
 */
class Leetify
{
    private $string = '';
    private $english = array("a", "e", "s", "S", "A", "o", "O", "t", "l", "ph", "y", "H", "W", "M", "D", "V", "x");
    private $leet = array("4", "3", "z", "Z", "4", "0", "0", "+", "1", "f", "j", "|-|", "\\/\\/", "|\\/|", "|)", "\\/", "><");
    private static $inst = null;
    private static function getInstance() {
        if(is_null(self::$inst)) {
            self::$inst = new self();
        }
        return self::$inst;
    }
    private function run($isEncode = false) {
        $out = '';
        if($this->string) {
            $dict = $isEncode ? $this->english : $this->leet;
            $dict_ = $isEncode ? $this->leet : $this->english;
            $flippedDict = array_flip($dict); // for good performance
            for($i = 0; $i < strlen($this->string); $i++) {
                $char = $this->string[$i];
                $out .= isset($flippedDict[$char]) ? $dict_[$flippedDict[$char]] : $char;
            }
        }
        return $out;
    }
    public function setString($string) {
        $t = self::getInstance();
        $t->string = $string;
        return $t;
    }
    public static function encode($string) {
        return self::getInstance()->setString($string)->run(true);
    }
    public static function decode($string) {
        return self::getInstance()->setString($string)->run();
    }
}