YouTipPhp Password_Verify
## PHP password_verify() Function
The `password_verify()` function in PHP is used to verify whether a given plain-text password matches a stored cryptographic hash. It is a crucial component of PHP's native password hashing API, designed to prevent security vulnerabilities such as timing attacks.
### Version Requirements
* **PHP 5 >= 5.5.0**
* **PHP 7**
* **PHP 8**
---
### Syntax
```php
bool password_verify ( string $password , string $hash )
```
#### Parameters
* **`password`**: The plain-text password provided by the user (e.g., from a login form).
* **`hash`**: The hashed password string against which to verify. This hash must be created using the [`password_hash()`](https://www.php.net/manual/en/function.password-hash.php) function.
#### Return Value
* Returns `true` if the password and hash match.
* Returns `false` if they do not match.
---
### Code Example
The following example demonstrates how to verify a plain-text password against a pre-calculated hash.
```php
```
#### Output
```text
Password is valid!
```
---
### Key Considerations & Best Practices
1. **Timing Attack Protection**
`password_verify()` is safe against timing attacks. It uses a constant-time comparison algorithm to ensure that the time taken to reject an incorrect password does not leak information about how close the guess was to the actual password.
2. **No Need to Manually Extract Salts**
The `$hash` string generated by `password_hash()` contains information about the algorithm, cost factor, and salt used during hashing. `password_verify()` automatically extracts these parameters from the hash string, so you do not need to store or manage salts separately in your database.
3. **Handling Algorithm Upgrades**
Over time, hardware becomes faster, and older hashing algorithms or cost factors may become insecure. It is highly recommended to pair `password_verify()` with `password_needs_rehash()`. If a user logs in successfully but the hash was generated using an outdated algorithm or cost, you can rehash the password and update the database seamlessly:
```php
if (password_verify($password, $storedHash)) {
// Check if the hash needs to be updated to a stronger algorithm/cost
if (password_needs_rehash($storedHash, PASSWORD_DEFAULT)) {
$newHash = password_hash($password, PASSWORD_DEFAULT);
// Update $newHash in your database for this user
}
// Proceed with logging the user in
}
```