What are common mistakes to avoid when using PHP to process form data?

One common mistake to avoid when processing form data in PHP is not properly sanitizing user input, which can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To prevent this, always use functions like `htmlspecialchars()` or `mysqli_real_escape_string()` to sanitize user input before using it in database queries or displaying it on the webpage. 

// Example of sanitizing user input before using it in a database query
$user_input = $_POST['user_input'];
$clean_input = mysqli_real_escape_string($connection, $user_input);

$query = "INSERT INTO table_name (column_name) VALUES ('$clean_input')";
mysqli_query($connection, $query);

Keywords

SQL injection cross-site scripting form validation htmlspecialchars error handling

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