Required file (Config) Undefined Property dsn

rpjd1

Looking at PDO tutorials on YouTube and PHP forums trying to figure this out.
This is my Config.php

$db = new Db;
    class Db
    {
        private $host;
        private $dbName;
        public $user;
        public $pass;

        public function Connect()
        {
            $this->host = 'localhost';
            $this->dbName = 'core';
            $this->user = 'root';
            $this->pass = '';

            try 
            {
                $dsn = "mysql:host=".$this->host.";dbName=".$this->dbName;
                $pdo = new PDO($dsn, $this->user, $this->pass);
                $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
            } 
            catch (PDOException $e) 
            {
                echo 'Error: '.$e->getMessage();
            }
        }
    }

This is Data.php

require 'Config.php';
$data = new Data;

class Data
{
    public function __construct()
    {
        global $db;
        try 
        {
            $pdo = new PDO($db->dsn,$db->user,$db->pass);
        } 
        catch (PDOException $e) 
        {
            echo 'Error' . $e->getMessage();
        }    
    }

I am getting Undefined Property Db::$dsn in Data.php $dsn is a variable in Config.php, so why is it saying Undefined Property? Appreciate any help, guidance with this.

NogDog

$dsn is not a class property, it's a local variable within the __construct() method. If you want to access it as a property, you need to define it as a public property and then assign the result of your PDO instantiation to $this->dsn.

That being said, I don't see why you need both the DB class and the Data class. Let's just simplify things (and avoid using global at all cost!) an do:

class Db extends PDO  // Assuming all we really need is a PDO object
{
    private $host = 'localhost';
    private $dbName = 'core';
    private $user = 'root';
    private $pass = 'pass';
    public function Connect()
    {
        $dsn = "mysql:host=".$this->host.";dbName=".$this->dbName;
        try {
            // now we can call the parent PDO constructor:
            parent::__construct($dsn, $this->user, $this->pass);
            $this->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
        } catch (PDOException $e) {
            echo 'Error: '.$e->getMessage();
        }
    }
}

Then if you do $data = new Db();, you're all set with $data being a PDO object with the desired DB connection.

rpjd1

Then I don't need this
public function __construct() { try { $pdo = new PDO($dsn,$user,$pass); } catch (PDOException $e) { echo 'Error' . $e->getMessage(); } }
in Data.php?

NogDog

rpjd1 Then I don't need this...in Data.php?

Assuming that Data class is something that wants to use the PDO object, I would recommend just passing that into its constructor:

require 'Config.php'; // creates the $db object
$data = new Data($db);  // pass it in to your Data object

class Data {
    private $db;
    public function __construct(PDO $db) {
        $this->db = $db;
    }
    public some_data_thing() {
        // Can now use $this->db to do any PDO stuff
    }
}

This avoids the use of global, which comes with some bad baggage, while also making the Data class's dependencies clear, which helps with maintenance and testing.

rpjd1

So, Config.php

`class Db extends PDO
{
private $host = 'localhost';
private $dbName = 'core';
private $user = 'root';
private $pass = 'pass';

public function Connect()
{
    $dsn = "mysql:host=".$this->host.";dbName=".$this->dbName;
    try {
        // now we can call the parent PDO constructor:
        parent::__construct($dsn, $this->user, $this->pass);
        $this->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
    } 
    catch (PDOException $e) 
    {
        echo 'Error: '.$e->getMessage();
    }
}

Data.php

`require 'Config.php';
$data = new Data($db);

class Data
{
public function __construct(PDO $db)
{
$this->db = $db;
}
public some_data_thing() {
// Can now use $this->db to do any PDO stuff
}
}`

__construct(PDO $db) doesn't match __contruct($dsn, $this->user, $this->pass) in Config.php
Notice: Undefined variable: db
Fatal error: Uncaught TypeError: Argument 1 passed to Data::__construct() must be an instance of PDO, null given

NogDog

The function name for the DB class needs to be __construct() (with double leading underscores), as you are overriding the constructor of the parent PDO class.

NogDog

PS: Using this forum's [code]...[/code] tags around your code blocks works much better than the </> button in the edit window (which really is only useful for making a bit of text mono-spaced within a sentence, unfortunately).

rpjd1

The method name for the Db class has double leading underscores. The construct() in Config has 3 PDO arguments, so shouldn't the parent method look like this?

__construct(PDO $dsn, PDO $user, PDO $pass)

NogDog

No, I'm calling the parent constructor via parent::__construct() within the child class's constructor, and at that time I'm using the values derived from the child class's properties as the 3 params to the parent.

Frankly, if the only reason for that Db class is to have those connection credentials, I might leave it out all together and just have them set in your config script as either $_ENV elements or just constants, then use them to directly create a PDO object. No big deal either way, but it might make it a bit simpler to configure things as/when any of those values change, or you want to have different values for different environments, etc.

rpjd1

The code in my Db class (Config.php)

try 
        {
            $dsn = "mysql:host=".$this->host.";dbName=".$this->dbName.";charset=".$this->charset;
            $pdo = new PDO($dsn, $user, $pass, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
            return $pdo;
        } 
        catch (PDOException $e) 
        {
            echo 'Error: '.$e->getMessage();
        }

This is the constructor in my Data class (Data.php)

public function __construct()
    {
        $pdo = new PDO($this->dsn,$user,$pass, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
    }

This line is giving me Undefined Property for dsn, Undefined variable for user and pass,
and Fatal error: Uncaught PDOException: invalid data source name

NogDog

rpjd1 This line is giving me Undefined Property for dsn, Undefined variable for user and pass

Then they have not been defined in that context -- but without seeing the class definition, I cannot be sure exactly why. But this is all trying to resolve a problem that shouldn't need solving: creating a database connection in more than one place. I strongly recommend creating your PDO object once, and then passing it in to any class or function that needs to use it. You almost always do not want to create multiple database connections within one PHP script.

rpjd1

I found a PHP tutorial on YouTube that works without using a PDO constructor or a connection class. I can work it for the time being.
This is the Config.php containing Db class

class Db extends PDO 
{
    private $host;
    private $dbName;
    private $user;
    private $pass;
    private $charset;

public function Connect()
{
    $this->host = "localhost";
    $this->user = "root";
    $this->pass = "";
    $this->dbName = "dbName";
    $this->charset = "utf8mb4";
    
    try 
    {

        $dsn = "mysql:host=".$this->host.";dbName=".$this->dbName.";charset=".$this->charset;
        $pdo = new PDO($dsn, $user, $pass, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
         return $pdo;
    } 
    catch (PDOException $e) 
    {
        echo 'Error: '.$e->getMessage();
    }
}
}

It's my understanding, using a connection class as above requires a constructor in the class that queries the database which is executed automatically when an object of the class is created.

In my webpage I have included Logic.php
I create a logic object $logic = new Logic;
Then I call a method in the Logic class $logic->MethodName();
If I do the same in Logic.php, include Data.php
create a Data object $data = new Data;
Then call a method in the Data from the Logic class $data->MethodName();
I get Undefined variable: data
This is confusing.

NogDog

rpjd1 It's my understanding, using a connection class as above requires a constructor in the class that queries the database which is executed automatically when an object of the class is created.

Not sure I follow.

Unless you're dealing with multiple databases, you only ever need one database connection. Since a PDO object is created with a database connection, you only need one PDO object in that case. So, what is the purpose of having this Db class that is extending PDO (and thus creates a PDO object by default), if inside of it you have a method that creates another PDO object? If the only reason is so that you can have your connection parameters built into it, then you can make it much simpler, as I suggested before:

class Db extends PDO {
    private $host = "localhost";
    private $user = "root";
    private $pass = "";
    private $dbName = "dbName";
    private $charset = "utf8mb4";
    public function __construct() {
        $dsn = "mysql:host={$this->host};dbName={$this->dbName};charset={$this->charset}";
        parent::__construct($dsn, $this->user, $this->pass, array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
    } 
}

// use it:
try {
    $pdo = new Db();
} catch (PDOException $e) {
    die('Error: '.$e->getMessage());
}

Now you can either use $pdo directly in your script, or pass it in as a parameter to any class or function that needs to talk to that database connection.

rpjd1

Thanks. My only problem is calling a method in the Data class.
If I create a Data object in Logic.php, (Data.php is included in Logic.php) then from the Logic class
$registered = $data->MethodName();
I get Undefined variable data.
I did the same thing to call a Logic method from my webpage, no issues.

NogDog

If you go back to https://www.webdeveloper.com/d/397887-required-file-config-undefined-property-dsn/4 I showed you how to pass your Db PDO object into any class that needs to use it. Then within that class you refer to $this->db (or whatever you prefer to name that class property) when you need to interact with your PDO object.

ginerjm

I just don't get the supposed "need" to create a class to implement something as simple as a database connection. Granted I am not an OOP guy but in this topic I see an awful lot of effort to simply connect to a db. Years ago I wrote a short block of code implementing a function that I then include in any script that needs a db. Call the function assigning its result to a var and use that everywhere I need it. I added a parm to the function to select the actual db name and another to alter the defined PDO options that I deem necessary and I can do anything with it.

I do hope the OP finally resolves this. Then I hope he looks at how much time he put into this effort and wonders why.

NogDog

ginerjm Yep, at least as I see it, the Db class is only a convenience(?) to deal with the configuration stuff -- and that can as easily be defined in the config php file, or a separate config.json file imported by it, whatever. Ultimately, whichever way you do it, just create ONE pdo object, and then pass it in to anything else that needs to use it, whether it's a class/object or a procedural function (or even lambda function). Don't keep creating more PDO objects whenever you want to talk to the database.