MySQL `Commands Out of Sync` Error: How to Resolve Sequential Query Issues with mysqli?

MySQL: Commands Out of Sync Error

Issue:

Users encounter the "Commands out of sync; you can't run this command now" error when attempting to execute multiple MySQL queries sequentially using mysqli.

Cause:

This error occurs because mysqli uses unbuffered queries by default for prepared statements. This means that the results of the first query must be retrieved before executing the next.

Solution:

There are two ways to resolve this issue:

Method 1: Fetching Results into an Array

Fetch the results of the first query into an array and loop through it. This approach involves the following steps:

1. Execute the first query.
2. Fetch all the rows into an array using mysqli_fetch_all() or $stmt->fetch_all().
3. Free the result using mysqli_free_result() or $stmt->free_result().
4. Execute the second query.

Method 2: Buffering Queries

Configure mysqli to buffer the queries using mysqli_stmt_store_result(). This approach involves the following steps:

1. Prepare the first query.
2. Execute the query.
3. Call $stmt->store_result() to buffer the results.
4. Execute the second query.

Implementation:

For example, to implement Method 2 in your provided code:

...
$countQuery = "SELECT ARTICLE_NO FROM AUCTIONS WHERE upper(ARTICLE_NAME) LIKE % ? %";
if ($numRecords = $con->prepare($countQuery)) {
    $numRecords->bind_param("s", $brand);
    $numRecords->execute();
    $numRecords->store_result(); // Buffer the results
    ...
}
...

Additional Notes:

• For non-prepared statements (using mysqli_query()), the default behavior is buffered.
• If you encounter the error while using a "SELECT *" query, it might be caused by a temporary table being created, which can cause inconsistencies in query order.

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