What are some common pitfalls to avoid when dealing with user input validation in PHP?

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

// Sanitize user input using htmlspecialchars
$user_input = htmlspecialchars($_POST['user_input']);
// Use the sanitized input in SQL query
$query = "SELECT * FROM users WHERE username = '$user_input'";
$result = mysqli_query($connection, $query);

Keywords

SQL injection cross-site scripting filter_var htmlentities validation errors

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