How to Fix the \'PHP Commands Out of Sync\' Error with MySQLi?

What is the "PHP Commands Out of Sync error"?

The "Commands out of sync" error in PHP/MySQLi occurs when multiple prepared statements are executed sequentially without properly clearing the results from the first statement. This error can disrupt the flow of your code and prevent you from retrieving data correctly.

Understanding the Cause of the Error

When a prepared statement is executed using mysqli::execute(), the MySQL server returns a result set. If you execute another statement without clearing this result set, the server becomes out of sync and raises the "Commands out of sync" error. This is because MySQL requires you to handle the previous result before executing a new statement.

Resolving the "Commands Out of Sync" Error

To resolve the error, you need to clear the result set from the first statement before executing the second statement. Here are some ways to achieve this:

• Use mysqli::free_result(): This method releases the memory associated with the result set, allowing the server to clear it.
• Use mysqli_stmt::close(): This method closes the prepared statement and automatically clears the result set.
• Use mysqli::more_results() and mysqli::next_result(): If you need to execute multiple statements in a loop, you can use more_results() to check if there are additional result sets and next_result() to clear them.

Additional Tips

• Always free or close result sets after executing a statement.
• Use mysqli::query() for executing non-prepared statements, as it automatically clears the result set for you.
• Avoid using LIMIT 1 in your prepared statements, as it can cause synchronization issues.
• If the error persists, check the MySQL server configuration for issues with concurrent queries or result set caching.

By following these steps, you can resolve the "Commands out of sync" error and ensure that your PHP/MySQLi code executes smoothly.

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