PHP - 在类中使用全局变量（致命错误）[关闭]

Question

I have a class.php file, in which I include a class from another file:

class.php:

 include($_SERVER['DOCUMENT_ROOT'] . "/includes/user.php");
 $user = new User;     

So, inside /includes/user.php is the $user class defined.

And in /includes/user.php there is a function named getSocialUser($username);:

function getSocialUser ($username)
{
    global $dbh;
    $stmt = $dbh->prepare("SELECT * FROM users WHERE username=:username");
    $stmt->bindParam(':username', $username);
    $stmt->execute();

    $udata = $stmt->fetch();

    if(count($udata) == 0)
        return false;

    return $udata;
}

(The $dbh holds the database value. I've tested it, and it does have a connection to the database)

However, I want to be able to use that function above inside the class.php file:

This is what I am doing now:

class.php:

 include($_SERVER['DOCUMENT_ROOT'] . "/includes/user.php");
 $user = new User;  


 Class feed {

   function randomFunction($username) {
   global $user;
   $username = "test";
   $viewuser = $user->getSocialUser($username);

   echo $viewuser['avatar'];
  }
}

The above code doesn't work. I get this error:

Fatal error: Call to a member function getSocialUser() on a non-object in/path/class.php on line 6

What am I doing wrong?

Answer 1

To start off, using GLOBAL is bad practice. Instead, add the database connection as a parameter, so change your function to the following

function getSocialUser ($dbh, $username)
{
    $stmt = $dbh->prepare("SELECT * FROM users WHERE username=:username");
    $stmt->bindParam(':username', $username);
    $stmt->execute();

    $udata = $stmt->fetch();

    if(count($udata) == 0)
        return false;

    return $udata;
}

Next, initiate the database connection and the user class in a construct of your class,

 Class feed {
     private $dbh;
     private $user;

     function __construct() {
         $this->dbh = new PDO('your data here');
         $this->user = new User();
     }

     function randomFunction($username) {
         $username = "test";
         $viewuser = $this->user->getSocialUser($this->dbh,$username);
         echo $viewuser['avatar'];
     }
 }