How can PHP developers ensure secure handling of user input data to prevent vulnerabilities?

PHP developers can ensure secure handling of user input data by using functions like `htmlspecialchars()` to prevent XSS attacks, `mysqli_real_escape_string()` to prevent SQL injection, and `filter_var()` to validate input data. Additionally, developers should always sanitize and validate user input before processing it to prevent vulnerabilities. 

// Example of using htmlspecialchars() to prevent XSS attacks
$user_input = "<script>alert('XSS attack');</script>";
$clean_input = htmlspecialchars($user_input);
echo $clean_input;

// Example of using mysqli_real_escape_string() to prevent SQL injection
$user_input = "'; DROP TABLE users; --";
$clean_input = mysqli_real_escape_string($connection, $user_input);
$query = "SELECT * FROM users WHERE username='$clean_input'";
$result = mysqli_query($connection, $query);

// Example of using filter_var() to validate input data
$user_email = "invalid_email";
if (filter_var($user_email, FILTER_VALIDATE_EMAIL)) {
    echo "Valid email address";
} else {
    echo "Invalid email address";
}

Keywords

SQL injection Cross-site scripting htmlspecialchars prepared statements input validation

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