Including parent objects in "require"d files

Question

Overview

I connect to a database in index.php, then import my classes.php file using require_once(). However, when connecting to the database, the database connection is undefined.

Code

index.php

$dbh = new PDO("mysql:host=$hostname;dbname=$dbname",$username,$password);
require_once("inc/classes.php");

/* ..... */

if($_POST["form"]=="login"){

    //Retrieve values
    $e = $_POST["email"];
    $p = $_POST["password"];

    //Data validation
    if(!filter_var($e, FILTER_VALIDATE_EMAIL)||strlen($e)<3) $errors->addError("email", "Please enter a valid email address.");
    if(strlen($p)<1) $errors->addError("password", "Please enter a valid password");
    $errors->killErrors();

    //Log user in
    $user = new User($e);
    if(!$user->login($p)) $errors->addError("form", "Incorrect username or password.");
    $errors->killErrors();

    exit("success");
}

inc/classes.php

class User
{
    public $id, $email, $data;

    public function __construct($e = null){

        if(isLoggedIn()){
            $stmt = $dbh->prepare("SELECT * FROM `users` WHERE `id`=? LIMIT 1");
            $stmt->execute(array($_SESSION["userid"]));
            $this->data = $stmt->fetch(PDO::FETCH_ASSOC);
        } else $this->email = $e;

    }

    public function login($p){
        //Perform database query for user
        $stmt = $dbh->prepare("SELECT `id`, `password` FROM `users` WHERE `email`=? LIMIT 1");
        $stmt->execute(array($this->email));
        if($stmt->rowCount()<1) return false;

        //Check password is correct
        $data = $stmt->fetch(PDO::FETCH_ASSOC);
        if(!password_verify($p, $data["password"])) return false;

        if(!$this->email) exit("User can only be logged in with an email address, not by User ID");

        $this->id = $data["id"];
        return $this->validate($this->id) ? true : false;
    }

}

Output

Notice: Undefined variable: dbh in /var/www/html/foo/public_html/bar/inc/classes.php on line 80

Fatal error: Call to a member function prepare() on null in /var/www/html/foo/public_html/bar/inc/classes.php on line 80

Line 80 is:

$stmt = $dbh->prepare("SELECT `id`, `password` FROM `users` WHERE `email`=? LIMIT 1");

Question

How can I include the database connection in index.php and have the classes.php file accept that PDO object?

You have to make it global $dbh; inside the function. It is a scope issue — Jay Blanchard
@JayBlanchard - directly inside the class or the individual function(s)? I've heard using global is not advised - is this still the case inside classes? — Ben
Done carefully it is OK, many use it too haphazardly and have a tendency to want to globalize all of their variables. I personally do it within the function to eliminate ambiguity. — Jay Blanchard
@JayBlanchard thanks - tested and working. If you post that as an answer I'll accept, cheers — Ben
You can also pass $dbh in function parameter as login($p,$dbh) get it usingfunction login($p,$dbh) — Saty

Jay Blanchard Jay Blanchard · Accepted Answer · 2016-02-02T13:06:29

You have to make your connection global:

global $dbh;

Because of scope. Done carefully it is OK to use global variables. Many use it too haphazardly and have a tendency to want to globalize all of their variables. I personally do it within the function inside the class to eliminate ambiguity.