What are potential pitfalls when validating user input in PHP forms?

One potential pitfall when validating user input in PHP forms is not properly sanitizing the input data, which can leave the application vulnerable to SQL injection attacks. To solve this issue, always sanitize user input using functions like `mysqli_real_escape_string()` or prepared statements before using it in database queries. 

// Example code snippet for sanitizing user input to prevent SQL injection
$user_input = $_POST['user_input'];
$clean_input = mysqli_real_escape_string($connection, $user_input);

// Now you can safely use $clean_input in your database query
$query = "SELECT * FROM users WHERE username = '$clean_input'";
$result = mysqli_query($connection, $query);

Keywords

XSS SQL injection filter_var htmlspecialchars validation errors

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