怎么禁止使用网络图片？

public function __construct($para = array()) {
                if(!empty($para)) {
                        $this->_table = $para['table'];
                        $this->_pk = $para['pk'];
                }
                if(isset($this->_pre_cache_key) && (($ttl = getglobal('setting/memory/'.$this->_table)) !== null || ($ttl = $this->_cache_ttl) !== null) && memory('check')) {
                        $this->_cache_ttl = $ttl;
                        $this->_allowmem = true;
                }
        $this->repair();//解决表是否崩溃，新加进去的代码
                $this->_init_extend();
                parent::__construct();
        }
    //解决表是否崩溃，新加进去的一个自己检查是否需要修复的代码
        public function repair() {
      $query1=DB::query('CHECK TABLE '.DB::table($this->_table));
          $checkresult =mysql_fetch_array($query1, MYSQL_ASSOC);
      //echo(DB::table($this->_table));
          //exit;                                
          if($checkresult['Msg_text'] != 'OK') {
          DB::query('REPAIR TABLE '.DB::table($this->_table));
                 }
                
        }