What are the potential pitfalls of not checking if a form has been submitted before inserting data into a database in PHP?

Potential pitfalls of not checking if a form has been submitted before inserting data into a database in PHP include duplicate entries being inserted, unnecessary database queries being executed, and potential security vulnerabilities such as SQL injection attacks. To solve this issue, you should always check if the form has been submitted before proceeding with database operations.

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Form has been submitted, proceed with database operations
    // Insert data into the database
} else {
    // Form has not been submitted, display form or do nothing
}