Common Errors When Upgrading from PHP 5.6 to 7.x

Upgrading from PHP 5.6 to PHP 7.x is a crucial step in enhancing the performance and security of your web applications. Since PHP 7 introduced considerable improvements, like reduced memory consumption and faster execution speeds, transitioning is incredibly beneficial. However, it is not without its pitfalls. In this blog post, we will discuss common errors encountered during this upgrade, best practices, and how you can address these issues effectively.

Why Upgrade to PHP 7.x?

Before diving into the errors, let’s explore why an upgrade to PHP 7.x is essential:

• Performance: PHP 7.x is statistically twice as fast as PHP 5.6, which leads to improved application response times.
• Memory Consumption: PHP 7 uses less memory than its predecessor, meaning better resource allocation for your applications.
• Type Declarations: PHP 7 introduced scalar type declarations and return type declarations, which enforce stricter typing—allowing for better error handling.
• Security: With each version, PHP enhances its security features, and using an outdated version exposes your application to vulnerabilities.

With these benefits in mind, let’s discuss common issues you may face during the upgrade.

1. Deprecated and Removed Functions

Issue

Certain functions prevalent in PHP 5.6 have been deprecated or removed entirely in PHP 7. For instance:

// Deprecated: The mysql extension is removed in PHP 7
$conn = mysql_connect("localhost", "user", "pass");

Solution

Update your code to use the mysqli or PDO extensions instead:

// Recommended: Use mysqli or PDO
$conn = new mysqli("localhost", "user", "pass", "database");

Why

The mysql extension is outdated and insecure. Migrating to mysqli or PDO helps optimize your code, ensures better security practices, and avoids disruptions with future PHP updates.

2. Changes to Error Handling

Issue

PHP 7 introduced a new error handling model. The E_ERROR, E_WARNING, etc., are handled through exceptions in many cases.

// Old-style error handling in PHP 5.6
if(!file_exists('somefile.txt')) {
    trigger_error('File not found!');
}

Solution

Leverage the new exception-based model:

// New-style error handling in PHP 7.x
if (!file_exists('somefile.txt')) {
    throw new Exception('File not found!');
}

Why

Using exceptions allows for more robust error handling logic. You can catch exceptions in a central location, making your application easier to debug and maintain.

3. Null Coalescing Operator

Issue

In older versions, checking for parameters often required multiple conditions:

// PHP 5.6 style
$username = isset($_GET['user']) ? $_GET['user'] : 'Guest';

Solution

PHP 7 introduced the null coalescing operator (??), which simplifies this:

// PHP 7.x style
$username = $_GET['user'] ?? 'Guest';

Why

By using the null coalescing operator, you make your code cleaner and easier to read. This operator simplifies your logic, reducing the chance of bugs related to undefined variables.

4. Type Hinting

Issue

The introduction of scalar type hints can create compatibility issues.

// PHP 5.6 style (no type hint)
function add($a, $b) {
   return $a + $b;
}

Solution

In PHP 7.x, make use of scalar type hints:

// PHP 7.x style (with type hinting)
function add(int $a, int $b): int {
    return $a + $b;
}

Why

Strict types help enforce better coding standards, resulting in fewer errors and more predictable code behavior. They provide a safety net against unintended data types being passed to methods.

5. Changes in the count() Function

Issue

In PHP 5.6, using count() on a non-countable variable would return 1. In PHP 7.2+, it will throw an error.

Solution

Ensure you're using count() only on arrays or Countable objects:

// Old-style check
if (is_array($items)) {
    echo count($items);
}

Why

Updating your checks ensures your code adheres to PHP 7's stricter checks, minimizing runtime errors.

6. Improved Random Functions

Issue

PHP 5.6's rand() and mt_rand() functions may not provide the security needed for current applications.

Solution

Use PHP 7's random_int() function for cryptographically secure random integers:

// Less secure way in PHP 5.6
$randomNumber = rand(1, 100);

// More secure way in PHP 7.x
$secureRandomNumber = random_int(1, 100);

Why

Security is paramount, especially for applications dealing with sensitive data. random_int() provides a much stronger layer of randomness compared to older functions.

To Wrap Things Up

Upgrading from PHP 5.6 to PHP 7.x can significantly enhance the performance, security, and maintainability of your applications. However, it is crucial to be prepared for common pitfalls that can surface during the transition.

Final Tips

• Test Thoroughly: Ensure you have a solid test suite. Run both unit tests and integration tests to check for regressions.
• Review Documentation: Familiarize yourself with the migration guides and official documentation from PHP: PHP Manual.
• Backup Your Code: Always maintain backups of your existing codebase before proceeding with an upgrade; better safe than sorry.

With careful planning and a proactive approach, upgrading can be a smooth process, allowing you to leverage the full advantages of PHP 7.x. By addressing these common errors, you can ensure your migration is successful, paving the way for a more robust application environment.

Happy coding!