If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example:

$unsafe_variable = $_POST['user_input']; 

mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");

That’s because the user can input something like value'); DROP TABLE table;--, and the query becomes:

INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')

What can be done to prevent this from happening ?

Solution 1

You basically have two options to achieve this:

1. Using PDO (for any supported database driver):

$stmt = $pdo->prepare('SELECT * FROM employees WHERE name = :name');

 $stmt->execute([ 'name' => $name ]);

 foreach ($stmt as $row) {
     // Do something with $row
 }


2. Using MySQLi (for MySQL):

$stmt = $dbConnection->prepare('SELECT * FROM employees WHERE name = ?');
 $stmt->bind_param('s', $name); // 's' specifies the variable type => 'string'

 $stmt->execute();

 $result = $stmt->get_result();
 while ($row = $result->fetch_assoc()) {
     // Do something with $row
 }