What are some potential pitfalls when trying to dynamically fill a select field in PHP based on user input?

When dynamically filling a select field in PHP based on user input, one potential pitfall is not properly sanitizing and validating the user input before using it to fetch data from a database. This can lead to security vulnerabilities such as SQL injection attacks. To solve this issue, always use prepared statements or parameterized queries to safely interact with the database. 

// Assuming $user_input contains the user input
$user_input = $_POST['user_input'];

// Sanitize and validate the user input
$user_input = filter_var($user_input, FILTER_SANITIZE_STRING);

// Prepare a SQL statement using a prepared statement
$stmt = $pdo->prepare("SELECT * FROM options WHERE category = :category");
$stmt->bindParam(':category', $user_input, PDO::PARAM_STR);
$stmt->execute();

// Dynamically fill the select field based on the query results
echo "<select>";
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
    echo "<option value='".$row['value']."'>".$row['label']."</option>";
}
echo "</select>";

Keywords

SQL injection XSS attacks form validation AJAX database queries

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