数组经print_r($arr,true)生成的字符串怎么还原成数组

class Trie {
  protected $dict = array();
  protected $buf = '';
  function set($word, $value='') {
    if(is_array($word)) foreach($word as $k=>$v) $this->set($k, $v);
    $p =& $this->dict;
    foreach(str_split($word) as $ch) {
        if(! isset($p[$ch])) $p[$ch] = array();
        $p =& $p[$ch];
    }
    $p['val'] = $value;
    return $this;
  }
  function parse($str) {
    $this->doc = $str;
    $this->len = strlen($str);
    $i = 0;
    while($i < $this->len) {
        $t = $this->find($this->dict, $i);
        if($t) {
            $i = $t;
            $this->buf = '';
        }else $this->buf .= $this->doc{$i++};
    }
  }
  protected function find(&$p, $i) {
    if($i >= $this->len) return $i;
    $t = 0;
    $n = $this->doc{$i};
    if( isset($p[$n]) ) $t = $this->find($p[$n], $i+1);
    if($t) return $t;
    if( isset($p['val']) ) {
        $ar = explode(',', $p['val']);
        call_user_func_array( array($this, array_shift($ar)), $ar );
        return $i;
    }
    return $t;
  }
  function __call($method, $param) {
    echo "****\n$this->buf 未定义方法:$method 参数:" . join(',', $param) . "
\n";
  }
}

------解决方案--------------------
探讨


先贴代码，有关算法问题我将另开贴讨论

Trie 键树类，基类PHP code
class Trie {
  protected $dict = array();
  protected $buf = '';
  function set($word, $value='') {
    if(is_array($word)) foreach($word as $k=>$v) $this->……