OOP致命错误：在不在对象上下文中时使用$ this

Question

I have following class.

    class User 
    {
        private $userRoles = array();

        //Populate the user object when it's created
        public function __construct($dbConn,$user_id)
        {

                self::loadRoles($dbConn,$user_id);//Initiate the userroles
        }

        //Fill the array with this user's roles, it's
        protected static function loadRoles($dbConn,$user_id)
        {
            $fetchRoles = $dbConn->prepare("SELECT tbl_user_role.role_id, tbl_roles.role_name FROM tbl_user_role JOIN tbl_roles ON tbl_user_role.role_id = tbl_roles.id WHERE tbl_user_role.user_id = :user_id");
            $fetchRoles->bindParam(':user_id', $user_id);
            $fetchRoles->execute();
                    //Populate the array
            while($row = $fetchRoles->fetch(PDO::FETCH_ASSOC))
            {

                $this->userRoles[$row["role_name"]] = Role::getRole($dbConn,$row["role_id"]); 
(Fatal error: Using $this when not in object context.)
            }
        } 
    }

Getting above error on this function protected static function loadRoles($dbConn,$user_id) . I am working with role based access control.

Please help me on this.

Answer 1

Static objects and functions do not have access to $this . If you're creating this with $user = new User() , then you need to change the call in your __construct() method:

public function __construct($dbConn,$user_id)
{
    $this->loadRoles($dbConn,$user_id);//Initiate the userroles
}

More information on static vs instantiated classes can be found in this question .

Edit As simon reminded me, the function itself would need to have the static keyword removed as well.

Answer 2

You are using $this but you are outside object. protected static function loadRoles($dbConn,$user_id) the static function doesn execute in the object so you have 2 opportunities: 1) return the roles and do whatever you want later:

$roles = array();
while($row = $fetchRoles->fetch(PDO::FETCH_ASSOC))
{
    $roles[$row["role_name"]] = Role::getRole($dbConn,$row["role_id"]); 
}

2) remove static keyword:

class User {
private $userRoles = array();

//Populate the user object when it's created
public function __construct($dbConn,$user_id)
{

    $this->loadRoles($dbConn,$user_id);//Initiate the userroles
}

//Fill the array with this user's roles, it's
protected function loadRoles($dbConn,$user_id)
{
    $fetchRoles = $dbConn->prepare("SELECT tbl_user_role.role_id, tbl_roles.role_name FROM tbl_user_role JOIN tbl_roles ON tbl_user_role.role_id = tbl_roles.id WHERE tbl_user_role.user_id = :user_id");
    $fetchRoles->bindParam(':user_id', $user_id);
    $fetchRoles->execute();
            //Populate the array
    while($row = $fetchRoles->fetch(PDO::FETCH_ASSOC))
    {
        $this->userRoles[$row["role_name"]] = Role::getRole($dbConn,$row["role_id"]); 
    }
} 

}