Error in PHP while inserting or selecting data from Database

Question

I am continuously getting error Undefined index in PHP while trying to login or sign up from my android app. I tried changing the PHP version but it didn't solve the problem. Here is the error I get in error_log :

[28-Aug-2017 15:15:33 America/Denver] PHP Notice:  Undefined index: full_name in /home2/heratarm/public_html/socialnetwork-api/Classes/user.php on line 33
[28-Aug-2017 15:15:33 America/Denver] PHP Notice:  Undefined index: username in /home2/heratarm/public_html/socialnetwork-api/Classes/user.php on line 34
[28-Aug-2017 15:15:33 America/Denver] PHP Notice:  Undefined index: email in /home2/heratarm/public_html/socialnetwork-api/Classes/user.php on line 35
[28-Aug-2017 15:15:33 America/Denver] PHP Notice:  Undefined index: password in /home2/heratarm/public_html/socialnetwork-api/Classes/user.php on line 36
[28-Aug-2017 15:15:57 America/Denver] PHP Notice:  Undefined index: username in /home2/heratarm/public_html/socialnetwork-api/Classes/user.php on line 12
[28-Aug-2017 15:15:57 America/Denver] PHP Notice:  Undefined index: password in /home2/heratarm/public_html/socialnetwork-api/Classes/user.php on line 13

And Here are my PHP codes:

class user
{

public function login()
{
    $data = [];
    require $_SERVER['DOCUMENT_ROOT'].'/socialnetwork-api/Config/db.php';
    $DB = new DB();$db=$DB->connection;
    $username =htmlentities($_POST['username'],ENT_QUOTES,"UTF-8");
    $password =htmlentities($_POST['password'],ENT_QUOTES,"UTF-8");
    $sql = "SELECT * FROM `tbl_users` WHERE `username`='$username' AND `password`='$password'";
    $result = $db->query($sql);
    $result = $result->fetch();
    if($result != null)
    {
        $data["result"]=$result['id'];
    }
    else
    {
        $data["result"]="0";
    }
    echo json_encode($data);
}

public function signup()
{
    $data = [];
    require $_SERVER['DOCUMENT_ROOT'].'/socialnetwork-api/Config/db.php';
    $DB = new DB();$db=$DB->connection;
    $fullname = htmlentities($_POST['full_name'],ENT_QUOTES,"UTF-8");
    $username = htmlentities($_POST['username'],ENT_QUOTES,"UTF-8");
    $email = $_POST['email'];
    $password = htmlentities($_POST['password'],ENT_QUOTES,"UTF-8");
    $sql = "SELECT * FROM `tbl_users` WHERE `username`='$username'";
    $result = $db->query($sql);
    $result = $result->fetch();
    if($result != null)
    {
        $data["result"] = "username";
    }
    else
    {
        $sql = "SELECT * FROM `tbl_users` WHERE `email`='$email'";
        $result = $db->query($sql);
        $result = $result->fetch();
        if($result != null)
        {
            $data["result"] = "email";
        }
        else
        {
            $sql = "INSERT INTO `tbl_users` (`full_name`,`username`,`email`,`password`) VALUES ('$fullname','$username','$email','$password')";
            $result = $db->prepare($sql);
            $result = $result->execute();

            if($result)
            {
                $data["result"]="1";
            }
            else
            {
                $data["result"]="0";
            }
        }
    }
    echo json_encode($data);
}

I hope someone helps me because I am not familiar with PHP so much and I need this for my project in University.

Answer 1

The undefined index errors correspond to your use of $_POST within your class. This means that when you call those class functions those values are not set.

Typically if you are going to use $_POST you have a form that calls your PHP script and each form input corresponds to a $_POST value.

For example, if you had a form with an input such as:

<input type="text" name="username" value="">

Then when the user submits the form you can get the value with $_POST['username'].

However, if you have no form submission then you will not have any $_POST values. Hence the undefined index errors.

An alternative approach is to have the values you need passed into the class methods. Then you need to make sure you pass those values when you call the method.

Example:

public function login($username = '', $password = '')
{
    $data = [];
    require $_SERVER['DOCUMENT_ROOT'].'/socialnetwork-api/Config/db.php';
    $DB = new DB();$db=$DB->connection;
    $username =htmlentities($username,ENT_QUOTES,"UTF-8");
    $password =htmlentities($password,ENT_QUOTES,"UTF-8");
    $sql = "SELECT * FROM `tbl_users` WHERE `username`='$username' AND `password`='$password'";
    $result = $db->query($sql);
    $result = $result->fetch();
    if($result != null)
    {
        $data["result"]=$result['id'];
    }
    else
    {
        $data["result"]="0";
    }
    echo json_encode($data);
}

Then you can pass the data in:

$class = new user();
$class->login($username, $password);

It's up to you to then pass in the values for $username and $password.