PHP8 | PDO → Getting a SQLSTATE[HY093]: Invalid parameter number on PDO Statement. It’s because of this.

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In the world of web development, bugs and issues are as certain as death and taxes (and both suck!). When you’re working with PHP and PDO to interact with databases, one error you might encounter is the SQLSTATE[HY093]: Invalid parameter number error. This error can be a bit puzzling, especially if you're sure you've provided all the necessary parameters in your query. Let's dive deeper into this error and how to resolve it effectively.

A Bit of History

In PHP 7, there was a subtle behavior when using PDO — if you used the same named parameter more than once in a query, it would silently fail. This means that while the query might have executed, it wasn’t necessarily providing the desired or expected results, and there was no explicit error to indicate a problem.

Come PHP 8, the PHP development team decided to make this scenario more transparent by introducing a clear error message when developers try to bind the same named parameter more than once. That’s the birth of our SQLSTATE[HY093]: Invalid parameter number error.

Understanding the Error

The error, as it suggests, indicates there’s a mismatch between placeholders in your SQL query and the parameters you’re trying to bind. One main reason behind this error is using the same named parameter multiple times within a single query.

For example, the problematic query:

SELECT * FROM company WHERE name = :company_name OR business_name = :company_name

Although it might seem logical to use :company_name for both columns (if you intend to search for the same term in both), PDO in PHP 8 doesn't see it that way.

The Solution

The solution is simple: ensure each named parameter in your SQL query is unique.

Here’s the corrected version of the query:

SELECT * FROM company WHERE name = :company_name OR business_name = :business_name

Then, when binding the parameters in PHP using PDO, you’d use:

$stmt = $pdo->prepare('SELECT * FROM company WHERE name = :company_name OR business_name = :business_name');
$stmt->execute([
'company_name' => $searchTerm, 
'business_name' => $searchTerm
]);

$searchTerm here represents the value you're searching for in both columns.

Conclusion

Programming, like any other discipline, evolves over time. As PHP transitioned from version 7 to 8, silent pitfalls were transformed into clear error messages to improve the developer experience. When dealing with PDO, always remember to use unique named parameters in your query to avoid the SQLSTATE[HY093]: Invalid parameter number error. This practice ensures more predictable behavior and saves time debugging ambiguous problems.

Happy Coding!