为什么mysql在PHP中调用过程后关闭数据库连接时报告“中止连接”

Question

I am running a server on Ubuntu 16.04 LTS with PHP 7.0 and MySQL 5.7.25. When running code snippet A MySQL logs "[Note] Aborted connection 23345 to db" upon trying to close the connection. This only happens when calling the stored procedure as seen in snippet A but not when directly executing the query as shown in snippet B.

Snippet A
<?php

    $database = new mysqli( 'localhost' , 'user' , 'test' , 'database' );

    $result = $database->query("CALL any_call();"); // returns true

    $result->close();

    $database->close();

?>

Snippet B
<?php

    $database = new mysqli( 'localhost' , 'user' , 'test' , 'database' );

    $result = $database->query("SELECT true;");

    $result->close();

    $database->close();

?>

Through trial and error I have found out that adding a $database->next_result(); solves the issue. But of course this can only be a workaround and not a solution to the actual problem.

Does anybody have an idea why this behavior occurs?

Thanks