PHP无法找到私有变量[关闭]

Question

For some reason PHP can't find my private variables.

I get following error message

*6 FastCGI sent in stderr: "PHP message: PHP Notice: Undefined variable: _database in /var/www/simple-blog/models/database.php on line 24 PHP message: PHP Fatal error: Uncaught Error: Cannot access empty property in /var/www/simple-blog/models/database.php:24

Line 24 is the line where I set $_database = $database.

class Database {

private $_database;
private $_mysqli;


public function connect(string $host, string $username, string $password, string $database) : bool
{
    $this->$_database = $database;

    $this->$_mysqli = new mysqli($host, $username, $password, $database);

    if ($this->$_mysqli->connect_error) {
        return false;
    } else {
        return true;
    }
}
...

I tried removing that aready, but then PHP can't find the variable $_mysqli

Answer 1

The way you used the variable is not correct. For more detail on php class variable have a look at http://php.net/manual/en/language.oop5.visibility.php

Change $this->$_database to $this->_database. Change $this->$_mysql to $this->_mysql