What are the best practices for constructing SQL queries dynamically in PHP based on user input from dropdown menus?

When constructing SQL queries dynamically in PHP based on user input from dropdown menus, it is important to sanitize and validate the user input to prevent SQL injection attacks. One approach is to use prepared statements with placeholders for user input values. This helps to separate the SQL query logic from user input, ensuring the query is safe and efficient. 

// Assuming $conn is the database connection object
// Assuming $dropdownValue is the user input from the dropdown menu

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

// Prepare SQL query with a placeholder for user input
$stmt = $conn->prepare("SELECT * FROM table_name WHERE column_name = ?");
$stmt->bind_param("s", $dropdownValue);
$stmt->execute();

// Fetch results
$result = $stmt->get_result();

// Process results as needed
while ($row = $result->fetch_assoc()) {
    // Do something with the data
}

// Close the statement and connection
$stmt->close();
$conn->close();

Keywords

SQL injection prepared statements PDO user input validation dynamic query building

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