PHP 点滴疑惑

1. 在数据库中，字段为NULL,可以使用empty()进行判断

   <?php
       $CONFIG['hostname'] = 'localhost';
       $CONFIG['username'] = 'root';
       $CONFIG['password'] = '';
       $CONFIG['database'] = 'test';
       $link = mysql_connect("localhost", $CONFIG['username'], $CONFIG['password']);
       mysql_select_db($CONFIG['database'], $link );
       $charset = mysql_query("SET NAMES 'utf8'", $link);
   
       $sql = "select init_weight from mytableas where id=3948";
   
       $query = mysql_query($sql);
       var_dump(mysql_fetch_assoc($query));
       $init_weight = mysql_fetch_assoc($query);
       var_dump(empty($init_weight['init_weight']));
   ?>