我如何获得COUNT（id）的值

Question

我遇到此对象的问题。我不知道（如果可能的话）如何获取的值COUNT(id)。我尝试将$req[0]->COUNT(id) but "COUNT()"其检测为功能。如何将其检测为钥匙？这是一个var_dump（$ req）：object(stdClass)[4]public 'COUNT(id)' => string '1' (length=1)的PHP$req = $db->query('SELECT COUNT(id) FROM `users` WHERE username ="'.$username.'" AND password = "'.$password.'"');if($req == 1){ $_SESSION['authentificated'] = true; $_SESSION['username'] = $username;}var_dump($req); 查询的输出应该为，0或者1用户是否已经注册。

Answer 1

这是您尚未绑定密钥的解决方案，请参见下文

 $req = $db->query('SELECT COUNT(id) as user_exists FROM `users` WHERE username 

="'.$username.'" AND password = "'.$password.'"');

if($req == 1){

    $_SESSION['authentificated'] = true;

    $_SESSION['username'] = $username;

}

var_dump($req); 

Answer 2

这里需要别名，否则别名将无法以您想要的方式捕获该计数值。

$req = $db->query('SELECT COUNT(id) cnt FROM `users` WHERE username ="'.$username.'" AND password = "'.$password.'"');

var_dump($req);