What are some potential pitfalls to avoid when creating a survey in PHP that requires user input and navigation through multiple questions?

One potential pitfall to avoid when creating a survey in PHP is not properly validating user input on each question before allowing navigation to the next question. This can lead to inconsistent data and errors in the survey results. To solve this, you can implement form validation for each question before allowing the user to proceed to the next one.

```php
// Example of form validation for a survey question in PHP

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate user input for question 1
    if (empty($_POST["question1"])) {
        $error = "Please answer question 1.";
    } else {
        // Store user response for question 1
        $question1_response = $_POST["question1"];
        
        // Redirect to next question or survey completion page
        header("Location: survey_question2.php");
        exit();
    }
}
```
In this code snippet, we check if the form has been submitted using the POST method. We then validate the user input for question 1 and store the response if it's valid. If the input is empty, we display an error message prompting the user to answer the question before proceeding. This helps ensure that the survey data is consistent and accurate.