Скачать или смотреть Solving the bind_param Mystery: Why Your MySQL Query Returns 0 Rows

Discover how to troubleshoot your MySQL and PHP queries when you encounter issues with `bind_param` returning zero rows. Learn the correct order of operations to resolve this common problem.
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This video is based on the question https://stackoverflow.com/q/64695139/ asked by the user 'SariHime' ( https://stackoverflow.com/u/8805962/ ) and on the answer https://stackoverflow.com/a/64695662/ provided by the user 'Dharman' ( https://stackoverflow.com/u/1839439/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

If you've ever faced the frustration of executing a MySQL query in PHP that should return a result but instead returns zero rows, you're not alone. This situation is particularly frustrating when you see other queries working perfectly, yet a very similar one fails to yield any results. This post will help you understand the nuances of using bind_param with mysqli to pinpoint why you're getting zero rows returned from your query.

Understanding the Problem

In the case we've encountered, the user has a SQL query that joins two tables—agents and returns. While the query functions correctly when tested directly against the database, it fails when using parameters bound via PHP. Here’s a quick snapshot of the scenario:

The query uses bind_param to bind a session-stored ID value.

Despite confirming that the ID works correctly with another query, it still fails to return results in this specific case.

Key Observations

When manually setting the ID, the query works.

The num_rows method returns zero.

The if condition checking for results always returns false.

These clues suggest that something is amiss in how the query executes compared to how the results are processed.

The Solution

After careful analysis, the primary issue lies in the order of operations concerning fetching results from the prepared statement. To fix this, follow these steps:

Step-by-Step Fix

Rearrange the Order of Method Calls: It's important to maintain the proper sequence when working with prepared statements in mysqli. Specifically, the fetch() method should be called after bind_result(). Here’s what the improved code looks like:

[[See Video to Reveal this Text or Code Snippet]]

Verify the Flow: After making this small adjustment, your logic should work seamlessly when you run the query. The num_rows function should now correctly reflect the number of rows retrieved from the database.

Close the Connection: Always remember to properly close your database connection with $con->close(); after you're done with your queries to free up resources.

Conclusion

When dealing with MySQL queries in PHP, small changes can have significant impacts on the results returned. Remember that the correct sequence of operations is crucial when binding parameters and fetching results. If you follow this improved approach, you should be able to resolve the issues you're facing with bind_param returning zero rows.

Feel free to reach out if you encounter any further issues or have additional questions. Happy coding!