Variable in Function not reachable

Question

i am writing a customer database. I've got a function to show all customers that looks like this.

<?php
class customer{

public function getAllCustomers(){
    global $database;
    $query = $database->query('SELECT * FROM hs_customers');
    $result = $database->statement->fetchAll();
    return $result;
}
}
?>

Until up here everything works well. Its connecting, im getting data and so on. The only thing i am unhappy with is i don't want the database name to be hardcoded inside the function, furthermore i want it to be replaced by a variable. So id did the following (as i did before, and it worked out well) but suddenly it wont replace the variable anymore?...

<?php
class customer{

private $customerDB = 'hs_customers';

public function getAllCustomers(){
    global $database;
    $query = $database->query('SELECT * FROM :db', array(':db' => $customerDB));
    $result = $database->statement->fetchAll();
    return $result;
}
}
?>

I guess i've got something wrong. Any advice? Thank you in advance.

Answer 1

You cannot use variable containers on syntax that is used by SQL, e.g. a table name or anything else related to the syntax like order, group etc. So in order to dynamically do this you have to escape the SQL string and use it like

$query = $database->query('SELECT * FROM '.($this->customerDB));

-- update for @TimG

And because you are in a class environment, the variable $customerDB should be treated as a class property. You have to use $this-> assignment to use any property of a class, unless it is static in that case, use self::.