Description:
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MySQLi prepared statement execution in a loop increases memory consumption rapidly constantly.

Test script:
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$now = microtime(true);
$db = new \Mysqli("localhost", "root", "password", "database", 3306);

$stmt = $db->prepare("SELECT * FROM someTable WHERE id=?");
$stmt->bind_param("i", $id);

for( $id=1; $id<1000; $id++ ) {
    $stmt->execute();
    $result = $stmt->get_result();
    $stmt->free_result();
}

echo "Time taken: ".(microtime(true)-$now)." seconds\n";
echo "Peak memory usage: ".number_format(memory_get_peak_usage())." bytes\n";

Expected result:
----------------
Memory usage should peak and stay around 400 KBs.

Actual result:
--------------
Memory usage constantly grows.