Uncaught Error: Call to a member function prepare() on null error

Question

I know there were a lot of answers related to this error, but I still don't know how to solve it... I'm trying to make the database connection, which would connect to the database and insert user's entered values in it and i got this error. I've created 2 files (with different classes):

Here is a connection file:

<?php
class Connection {
    // Setting Database Source Name (DSN)
 public function __construct() {
$dsn = 'mysql:host=localhost;dbname=employees';
// Setting options
$options = array (PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION);
// Making the connection to the database
try {
$this->dbh = new PDO($dsn, 'root', '', $options); 
}
catch (PDOException $e) {
$this->error = $e->getMessage();
        }
    }
}
$connection = new connection();
?>

And here is users.php file:

<?php
include 'connection.php';
class Users {
public $name;
public $surname;
public $employmentDate;
public function __construct()
{
if(isset($_POST['Submit'])) {
$this->name = $_POST['name'];
$this->surname = $_POST['surname'];
$this->employmentDate = $_POST['employmentDate'];
}
}
// Inserting users values to the database table
public function insertUserValues() {
 $stmt= 'INSERT INTO employee (name,surname,employment_date) VALUES (:name,:surname,:employmentDate)';
 $stmt = $this->dbh->prepare();
 $stmt->bindValue(':name',$name, PDO::PARAM_STR);
 $stmt->bindValue(':surname',$surname, PDO::PARAM_STR);
 $stmt->bindValue(':employmenDate',$employmentDate, PDO::PARAM_STR);
 $stmt->execute([$this->name,$this->surname,$this->employmentDate]);
}
}
$users = new Users();
$users->insertUserValues();
?>

I guess there are some mistakes in code structure, but I'm just learning, so. The code line which throws the error 18 line in users.php file:

$stmt = $this->dbh->prepare();

Please someone tell me where I am doing a mistake, thank you for any help.

Guillaume Sainthillier · Accepted Answer · 2017-03-07T09:37:43.350

1

You just have somes mistakes in your code. Try to use this lines :

Connection file :

<?php
class Connection {
    public $dbh;

    // Setting Database Source Name (DSN)
    public function __construct() {
        $dsn = 'mysql:host=localhost;dbname=employees';
        // Setting options
        $options = array (PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION);
        // Making the connection to the database
        try {
            $this->dbh = new PDO($dsn, 'root', '', $options); 
        }
        catch (PDOException $e) {
            $this->error = $e->getMessage();
        }
    }
}

$connection = new connection();

users.php file :

<?php

include 'connection.php';
class Users {
    public $name;
    public $surname;
    public $employmentDate;
    public $connection;

    public function __construct($connection)
    {
        $this->connection = $connection;
        if(isset($_POST['Submit'])) {
            $this->name = $_POST['name'];
            $this->surname = $_POST['surname'];
            $this->employmentDate = $_POST['employmentDate'];
        }
    }

    // Inserting users values to the database table
    public function insertUserValues() {
        $query = 'INSERT INTO employee (name,surname,employment_date) VALUES (:name,:surname,:employmentDate)';
        $stmt = $this->connection->dbh->prepare($query);
        $stmt->bindValue(':name',$this->name, PDO::PARAM_STR);
        $stmt->bindValue(':surname',$this->surname, PDO::PARAM_STR);
        $stmt->bindValue(':employmentDate',$this->employmentDate, PDO::PARAM_STR);
        $stmt->execute();
    }
}   

$users = new Users($connection);
$users->insertUserValues();

Explanations :

You have to pass the $connection variable to your users class (or import it with global $connection;)
Your connection file has to make visible the dbh property, otherwise you will not be able to make any query on your database
PDO prepare() method is waiting for a query in first argument
You don't need to pass an array to execute() method if you already have binded your values before

edited Mar 07 '17 at 09:37

answered Mar 07 '17 at 08:42

Guillaume Sainthillier

1,655
1
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13

I still got the same error. It also says that $dbh property in the same line is undefined – user7435747 Mar 07 '17 at 08:44
Just updated my answer. Hope this will help ! – Guillaume Sainthillier Mar 07 '17 at 08:55
Thank you, at least it's passing to the next line errors :) – user7435747 Mar 07 '17 at 09:09
could you help me to solve one more error? It's in the execute statement and it says "execute() expects parameter 1 to be array, string given". My code line is: `$stmt->execute($query);` – user7435747 Mar 07 '17 at 09:21
Keep your stmt->bindValue() calls and remove the parameter to execute() ;-) execute don't need any params if you already bind all the values – Guillaume Sainthillier Mar 07 '17 at 09:28
But if I am removing execute() parameter it says 'parameter was not defined' in that line... – user7435747 Mar 07 '17 at 09:30
You have a typo in the last bindValue. replace :employmenDate with :employmentDate ;-) – Guillaume Sainthillier Mar 07 '17 at 09:31
Meh, I've edited the line, but it's still printing 'Column 'name' cannot be null'. Thank you for the help anyway m8, good luck. :) – user7435747 Mar 07 '17 at 09:36
Got it. Just updated my answer, you had to replace $name by $this->name and so on ! – Guillaume Sainthillier Mar 07 '17 at 09:38
To help you to find this problems, you can add error_reporting(E_ALL); and ini_set('display_errors', 1); at the start of your PHP files – Guillaume Sainthillier Mar 07 '17 at 09:39

score 0 · Answer 2 · answered Mar 07 '17 at 08:43

0

You are referring to $this from outside the class scope. You probably want

$connection->dbh->prepare();

answered Mar 07 '17 at 08:43

Bart Friederichs

33,050
15
95
195

I've just changed my line with yours, but it didn't helped and I got one new eror, which says that connection is undefined – user7435747 Mar 07 '17 at 08:48
It is, because you use it in the function and it is a global. Add `global $connection` to the top of your function. You issue here is not about PDO, but about scope and variables. Make sure you understand PHP basics before you continue with database stuff. – Bart Friederichs Mar 07 '17 at 08:55

score 0 · Answer 3 · answered Mar 07 '17 at 08:56

You could make your connection class to a singleton:

class Connection {

    private static $instance = null;

    // Setting Database Source Name (DSN)
    public function __construct() {
       $dsn = 'mysql:host=localhost;dbname=employees';
      // Setting options
      $options = array (PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION);
     // Making the connection to the database
     try {
        $this->dbh = new PDO($dsn, 'root', '', $options); 
     } catch (PDOException $e) {
       $this->error = $e->getMessage();
        }
    }

    public static function __callStatic($name, $args) {
        if (self::$instance == null) {
             self::$instance = new self();
        }
        call_user_func_array([ self::$instance->dbh, $name], $args);
    }   

}

Then use it as follows:

 Connection::prepare(); //or connection::any_pdo_function

Uncaught Error: Call to a member function prepare() on null error

3 Answers3

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