Question

my sample is good or not?
I have a good connection to the database, or too should be in the class?

Thanks

<?php
mysql_connect('localhost','root','admin');
mysql_select_db('test');

class UserDisplay
{
    function getDisplayName()
    {
        $sql = 'select first_name, last_name, display_name from users where user_id = "3"';
        $results = mysql_query($sql);
        $row = mysql_fetch_array($results);
        $this->user_id = $user_id;

        return $this->user_id;
    }
}

class UserInsert

    function InsertName($name)
    {
        mysql_query("INSERT INTO Persons (first_name)VALUES ('".$name."')");
    }
}

$userD = new UserDisplay();
echo "User known as: " . $userD->getDisplayName() . "\n";

$userI = new UserInsert();
$userI->InsertName("Peter");
?>

Answer 1

Probably be better off just making them functions, instead of wrapping them up in classes. Extract all of it, except the last into it’s own php file. You forgot to extract display name from $user

// myFunctions.php
<?php
function connectDb() {
    mysql_connect('localhost', 'root', 'admin');
    mysql_select_db('test');
}

function closeDb() {
    mysql_close();
}

function displayName() {
    $sql = 'select first_name, last_name, display_name from users where user_id = "3"';
    $results = mysql_query($sql);
    $user = mysql_fetch_array($results);
    return $user['display_name'];
}

function insertFirstName($name) {
    mysql_query("INSERT INTO Persons (first_name)VALUES ('" . $name . "')");
}
?>

// index.php
<?php
require_once 'myFunctions.php';

connectDb();
echo "User known as: " . displayName() . "\n";
insertFirstName("Peter");
closeDb();
?>

But if you insist on using classes:

// User.php
<?php
class User {

    private function connectDb() {
        mysql_connect('localhost', 'root', 'admin');
        mysql_select_db('test');
    }

    private function closeDb() {
        mysql_close();
    }

    function displayName() {
        $this->connectDB();

        $sql = 'select first_name, last_name, display_name from users where user_id = "3"';
        $results = mysql_query($sql);
        $user = mysql_fetch_array($results);

        $this->closeDB();

        return $user['display_name'];
    }

    function insertFirstName($name) {
        $this->connectDB();
        mysql_query("INSERT INTO Persons (first_name)VALUES ('" . $name . "')");
        $this->closeDB();
    }
}
?>

// index.php
<?php
require_once 'User.php';

$user = new User;
echo "User known as: " . $user->displayName() . "\n";
$user->insertFirstName("Peter");
?>

Actually not bad. abstracted out the db connection and close.