What are the potential security risks associated with copying and pasting code from external sources without full understanding in PHP development?

Copying and pasting code from external sources without full understanding can introduce security risks such as vulnerabilities, backdoors, and malicious code. To mitigate these risks, developers should always review and understand the code they are using, ensure it comes from trusted sources, and validate input data to prevent injection attacks.

// Example of validating input data to prevent SQL injection
$user_input = $_POST['user_input'];
$clean_input = mysqli_real_escape_string($connection, $user_input);

// Use $clean_input in your SQL query to prevent SQL injection