How can the use of variable interpolation in PHP impact the functionality of a script that retrieves data based on user input?

Variable interpolation in PHP can impact the functionality of a script that retrieves data based on user input if the user input is directly concatenated into a SQL query string. This can lead to SQL injection attacks where malicious users input SQL commands to manipulate the database. To prevent this, it is recommended to use prepared statements with parameterized queries to securely retrieve data based on user input.

// Example of using prepared statements to retrieve data based on user input
$user_input = $_GET['user_input'];

// Prepare the SQL query with a placeholder for the user input
$stmt = $pdo->prepare("SELECT * FROM table WHERE column = :user_input");

// Bind the user input to the placeholder
$stmt->bindParam(':user_input', $user_input);

// Execute the query
$stmt->execute();

// Fetch the results
$results = $stmt->fetchAll();