PHP mysqli 插入不起作用

啊，我无法理解这一点。 我有一个连接到 mySQL 数据库：

function db_connect() {
  static $connection;
  if(!isset($connection)) {
    $config = parse_ini_file($_SERVER['DOCUMENT_ROOT'] . "/cfi/config.ini");
    $connection = mysqli_connect('localhost',$config['username'],$config['password'],$config['dbname']);    
  }

  if($connection === false) {
    return mysqli_connect_error();
  }
  return $connection;
}

我像这样运行它：

$connection = db_connect();

然后我尝试像这样运行一个插入：

if (mysqli_query($connection, "INSERT INTO pending ('aw_id','in_stock') VALUES ('1','yes')")) {
  echo "success";
} else {
  echo "fail";
}

但它总是失败...我错过了什么？

我不确定它是否有帮助，但$connection var_dump是：

object(mysqli)#1 (19) { ["affected_rows"]=> int(0) ["client_info"]=> string(79) "mysqlnd 5.0.11-dev - 20120503 - $Id: bf9ad53b11c9a57efdb1057292d73b928b8c5c77 $" ["client_version"]=> int(50011) ["connect_errno"]=> int(0) ["connect_error"]=> NULL ["errno"]=> int(0) ["error"]=> string(0) "" ["error_list"]=> array(0) { } ["field_count"]=> int(0) ["host_info"]=> string(25) "Localhost via UNIX socket" ["info"]=> NULL ["insert_id"]=> int(0) ["server_info"]=> string(6) "5.6.23" ["server_version"]=> int(50623) ["stat"]=> string(147) "Uptime: 684382 Threads: 3 Questions: 5532897 Slow queries: 14 Opens: 287168 Flush tables: 37 Open tables: 1024 Queries per second avg: 8.084" ["sqlstate"]=> string(5) "00000" ["protocol_version"]=> int(10) ["thread_id"]=> int(184926) ["warning_count"]=> int(0) } 

嘭！！