What are the differences between using $_GET and $_POST in PHP?

When working with forms in PHP, the main difference between using $_GET and $_POST is how the data is sent to the server. $_GET sends data through the URL, which can be seen in the browser's address bar, while $_POST sends data through the HTTP request body, which is not visible to the user. To solve this issue, you should use $_POST when handling sensitive information, such as passwords or personal details, to ensure that the data is not exposed in the URL. On the other hand, you can use $_GET when you want the data to be easily accessible or shareable through the URL.

```php
<form method="post" action="process_form.php">
  <label for="username">Username:</label>
  <input type="text" id="username" name="username">
  
  <label for="password">Password:</label>
  <input type="password" id="password" name="password">
  
  <input type="submit" value="Submit">
</form>
```

In the above code snippet, we are using the POST method to send the form data to the server securely. This ensures that sensitive information like the password is not exposed in the URL.