Commands out of sync; you can't run this command now1

Question

I am trying to execute my php code, which calls two mysql queries via mysqli, and get the titular error.

Here is the code I am using

<?php
$con = mysqli_connect("localhost", "user", "password", "db");
if (!$con) {
    echo "Can't connect to MySQL Server. Errorcode: %s\n". mysqli_connect_error();
    exit;
}
$con->query("SET NAMES 'utf8'");
$brand ="o";
$countQuery = "SELECT ARTICLE_NO FROM AUCTIONS WHERE upper(ARTICLE_NAME) LIKE % ? %";
if ($numRecords = $con->prepare($countQuery)) {
    $numRecords->bind_param("s", $brand);
    $numRecords->execute();
    $data = $con->query($countQuery) or die(print_r($con->error));
    $rowcount = $data->num_rows;
    $rows = getRowsByArticleSearch("test", "Auctions", " ");
    $last = ceil($rowcount/$page_rows);
}  else {

print_r($con->error);
}
foreach ($rows as $row) {
    $pk = $row['ARTICLE_NO'];
    echo '<tr>' . "\n";
    echo '<td><a href="#" onclick="updateByPk(\'Layer2\', \'' . $pk . '\')">'.$row['USERNAME'].'</a></td>' . "\n";
    echo '<td><a href="#" onclick="updateByPk(\'Layer2\', \'' . $pk . '\')">'.$row['shortDate'].'</a></td>' . "\n";
    echo '<td><a href="#" onclick="deleterec(\'Layer2\', \'' . $pk . '\')">DELETE RECORD</a></td>' . "\n";
    echo '</tr>' . "\n";
}
function getRowsByArticleSearch($searchString, $table, $max) {
    $con = mysqli_connect("localhost", "user", "password", "db");
    $recordsQuery = "SELECT ARTICLE_NO, USERNAME, ACCESSSTARTS, ARTICLE_NAME, date_format(str_to_date(ACCESSSTARTS, '%d/%m/%Y %k:%i:%s'), '%d %m %Y' ) AS shortDate FROM AUCTIONS WHERE upper(ARTICLE_NAME) LIKE '%?%' ORDER BY str_to_date(ACCESSSTARTS, '%d/%m/%Y %k:%i:%s')" . $max;
    if ($getRecords = $con->prepare($recordsQuery)) {
     $getRecords->bind_param("s", $searchString);
     $getRecords->execute();
     $getRecords->bind_result($ARTICLE_NO, $USERNAME, $ACCESSSTARTS, $ARTICLE_NAME, $shortDate);
     while ($getRecords->fetch()) {
      $result = $con->query($recordsQuery);
      $rows = array();
      while($row = $result->fetch_assoc()) {
       $rows[] = $row;
      }
      return $rows;
     }
    }
}

I have tried reading up on this, but I am unsure of what to do. I have read about store result and free result, however these have made no difference when using them. I am unsure at exactly which point this error is being caused, and would like to know why it is being caused, and how to fix it.

Going by my debug statements, the first if loop for countQuery is not even being entered, because of an error in my sql syntax near near '% ? %'. However if I just select * instead of trying to limit based on a LIKE clause, I still get the command out of sync error.

Answer 1

What's the version of your MySQL database and provider?

Answer 2

I think the problem is that you're making a new connection in the function, and then not closing it at the end. Why don't you try passing in the existing connection and re-using it?

Another possibility is that you're returning out of the middle of a while loop fetching. You never complete that outer fetch.

Answer 3

You can't have two simultaneous queries because mysqli uses unbuffered queries by default (for prepared statements; it's the opposite for vanilla mysql_query). You can either fetch the first one into an array and loop through that, or tell mysqli to buffer the queries (using $stmt->store_result()).

See here for details.

Answer 4

The problem is the MySQL client C library, which most MySQL APIs are built on. The problem is that the C library doesn't support simultaneous execution of queries, so all APIs built on top of that also do not. Even if you use unbuffered queries. This is one reason why the asynchronous MySQL API was written. It communicates directly with the MySQL server using TCP and the wire-protocol does support simultaneous queries.

Your solution is to either modify the algorithm so you don't need to have both in progress at once, or change them to use buffered queries, which is probably one of the original reasons for their existence in the C library (the other is to provide a kind of cursor).

Answer 5

I solved this problem in my C application - here's how I did it:

(1) [quoting from mysql forums] -- "This error results when you terminate your query with a semicolon delimiter inside the application. While it is required to terminate a query with a semicolon delimiter when executing it from the command line or in the query browser, remove the delimiter from the query inside your application."

(2) After running my query and dealing with the results [C API: mysql_store_result()], I iterate over any further potentially pending results that occurs via multiple SQL statement execution such as two or more select statements (back to back without dealing with the results). The fact is that my procedures don't return multiple results but the database doesn't know that until I execute: [C API: mysql_next_result()]. I do this in a loop (for good measure) until it returns non-zero. That's when the current connection handler knows it's okay to execute another query (I cache my handlers to minimize connection overhead).

This is the loop I use:

for(; mysql_next_result(mysql_handler) == 0;) 
  /* do nothing */;

I don't know PHP but I'm sure it has something similar.