Is this bad practice for inserting data into db? - php

Question

I have this function that inserts data from a checkbox into my sql database and it works just find, but Im pretty new to this so I would like to know if there is a better/safer (from sql injections) way to do this. I know I should be using PDO with prepared statements, but that is something I am tackling later.
Here is the form that produces the html checkboxes:
<form action="" method="post">
<?php
if(empty($clients) === true){
echo '<p>You do not have any clients yet.</p>';
}
else
{
foreach($clients as $client){
echo'
<input type="checkbox" name="client_data[]" value="'.$_SESSION['user_id'].'|'.$class_id.'|'.$client['first_name'].'|'.$client['nickname'].'|'.$client['last_name'].'">
'.$client['first_name'].' ('.$client['nickname'].') '.$client['last_name'].'
<br />';
} // foreach($client
} // if empty
?>
Here is the php that calls the function:
if (isset($_POST['exist_to_class'])){
if (empty($_POST['client_data']) === true){
$errors [] = 'You much select a client to be added to the class.';
} else {
if (isset($_POST['client_data']) && !empty($_POST['client_data']));
foreach ($_POST['client_data'] as $cd){
exist_client_to_class($cd);
header('Location: view_class.php?class_id='.$class_id.' ');
} // foreach $cd
} // else
} //isset
And here is my function that inserts the data into the db:
// add existing client to class ----------------------------------------------------
function exist_client_to_class($cd){
list($user_id, $class_id, $first_name, $last_name, $nickname) = explode('|', $cd);
mysql_query("INSERT INTO `clients` (user_id, class_id, first_name, last_name, nickname, date)
VALUES('$user_id', '$class_id', '$first_name', '$last_name', '$nickname', CURDATE())");
}
First stab at a PDO prepared statement:UPDATE
function exist_client_to_class($cd){
try{
$stmt = $conn->prepare('INSERT INTO clients
(user_id, class_id, first_name, last_name, nickname, date)
VALUES (:user_id, :class_id, :first_name, :last_name, :nickname, CURDATE())
');
list($user_id, $class_id, $first_name, $last_name, $nickname) = explode('|', $cd);
$stmt->execute(array(
':user_id' => $user_id,
':class_id' => $class_id,
':first_name' => $first_name,
':last_name' => $last_name,
':nickname' => $nickname
)
);
}
catch(PDOException $e) {
echo 'Error: ' . $e->getMessage();
}
}
Here is the db connect file:
//PDO database connect
try {
$conn = new PDO('mysql:host=localhost;dbname=customn7_cm', '**********', '**********');
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$conn->exec("SET CHARACTER SET utf8");
} catch(PDOException $e) {
echo 'ERROR: ' . $e->getMessage();
}

Answer 1

To put simply, Yes.
You aren't sanitizing or escaping your user data in anyway. you are using the old mysql_* community deprecated functions. You're best bet is to start using PDO or Mysqli
Read this article: PHP Database Access: Are You Doing It Correctly?

Answer 2

This works for most sql injections: (from php.net)
decleration:
string mysql_real_escape_string ( string $unescaped_string [, resource $link_identifier = NULL ] )
// Connect
$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password') OR die(mysql_error());
// Query
$query = sprintf("SELECT * FROM users WHERE user='%s' AND password='%s'",
mysql_real_escape_string($user),
mysql_real_escape_string($password));