Cleansing User Passwords


When it comes to storing user passwords securely, the process involves more than just hashing the passwords. Before hashing, it is essential to cleanse or sanitize the user-provided passwords to prevent any vulnerabilities such as SQL injection or cross-site scripting (XSS) attacks. In this article, we will explore the best practices for cleansing user passwords in PHP before hashing and storing them in the database.

Understanding the Importance of Password Cleansing

Before we delve into the specifics of password cleansing, let's first understand why it is necessary. User-provided data, including passwords, can contain special characters, escape characters, or malicious input. If not properly cleansed, these inputs can lead to vulnerabilities like SQL injection or XSS attacks. By cleansing the passwords, we ensure that they are safe to use and store in the database.

Common Password Cleansing Techniques

There are several techniques available in PHP to cleanse user passwords. Let's discuss some of the most commonly used techniques:

1. addslashes()

The addslashes() function is commonly used to add escape characters before special characters in a string. However, using this function alone is not sufficient to cleanse passwords, as it doesn't handle all possible escape characters. Therefore, it is not recommended as the sole method for password cleansing.

$password = addslashes($_POST['password']);

2. htmlspecialchars()

The htmlspecialchars() function is used to convert special characters to their HTML entities. While this function can help prevent XSS attacks, it should not be used solely for password cleansing. It is primarily used to sanitize user input that will be displayed on HTML pages.

$password = htmlspecialchars($_POST['password'], ENT_QUOTES);

3. Filter Input and Filtering Functions

PHP provides the filter_input() function to validate and cleanse user input. It can be used to filter and sanitize the password input using various pre-defined filters such as FILTER_SANITIZE_STRING and FILTER_SANITIZE_SPECIAL_CHARS.

$password = filter_input(INPUT_POST, 'password', FILTER_SANITIZE_STRING);

Preventing SQL Injection

SQL injection is a common vulnerability that can occur when user input is not properly handled. To prevent SQL injection when storing passwords in the database, it is important to use prepared statements with parameterized queries. Prepared statements automatically escape special characters, providing an additional layer of protection.

$stmt = $pdo->prepare("INSERT INTO users (username, password) VALUES (:username, :password)");
$stmt->bindParam(':username', $_POST['username']);
$stmt->bindParam(':password', $password);

Hashing User Passwords

After properly cleansing the user passwords, the next step is to hash them before storing in the database. Hashing passwords is a one-way process, making it nearly impossible to reverse-engineer the original password from the hash.

PHP provides built-in functions like password_hash() and password_verify() to securely hash and verify passwords. It is recommended to use the PASSWORD_BCRYPT algorithm for hashing passwords, as it is currently considered the most secure algorithm.

$hashedPassword = password_hash($password, PASSWORD_BCRYPT);


Ensuring the security of user passwords is crucial for any application that handles user data. By properly cleansing and hashing passwords, you can mitigate the risk of data breaches and unauthorized access. Remember to use a combination of password cleansing techniques and prepared statements with parameterized queries to prevent SQL injection attacks. Additionally, always use a secure hashing algorithm like PASSWORD_BCRYPT for hashing passwords.