Memory leak when using prepared statements without arguments

[maxscale]

threads=1

[Galera Monitor]

type=monitor

module=galeramon

servers=server1,server2,server3

user=monitor

passwd=password

monitor_interval=1000

[qla]

type=filter

module=qlafilter

options=/tmp/QueryLog

[RW Split Router]

type=service

router=readwritesplit

servers=server1,server2,server3

user=maxscale

passwd=password

localhost_match_wildcard_host=1

max_slave_connections=100%

router_options=slave_selection_criteria=LEAST_CURRENT_OPERATIONS,disable_sescmd_history=true

[CLI]

type=service

router=cli

[RW Split Listener]

type=listener

service=RW Split Router

protocol=MySQLClient

socket=/tmp/maxscale.sock

port=3306

[CLI Listener]

type=listener

service=CLI

protocol=maxscaled

port=6603

[server1]

type=server

address=galera1

port=3306

protocol=MySQLBackend

[server2]

type=server

address=galera2

port=3306

protocol=MySQLBackend

[server3]

type=server

address=galera3

port=3306

protocol=MySQLBackend

<?php

$isParent    = true;

$children    = array();

$start        = microtime( true);

$stmtCount = (int)$_SERVER[ "argv" ][ 1 ];

$procCount = (int)$_SERVER[ "argv" ][ 2 ];

$type = $_SERVER[ "argv" ][ 3 ] ?: 'maxscale';

$ceiling = $procCount;

for ( $i = 0; (( $i < $ceiling) && ( $isParent)); $i++) {

    $pid = pcntl_fork();

    if ( $pid === 0) {

        $isParent = false;

    } elseif ( $pid != -1) {

        $children[] = $pid;

    }

}

function getStatus( $stmtType ) {

    $res = 0;

    for( $i = 1; $i <= 3; $i++ ) {

        $dsn = "mysql:host=galera{$i};dbname=database";

        $dbh = new PDO( $dsn, 'queryuser', 'password' );

        $stmt = $dbh->query( "show global status like 'Com_stmt_{$stmtType}'" );

        $stmt->execute();

        $stmtRes = $stmt->fetch( PDO::FETCH_ASSOC );

        $res += (int)$stmtRes[ 'Value' ];

    }

    return $res;

}

function getDiff() {

    $closed = getStatus( 'close' );

    $prepared = getStatus( 'prepare' );

    return $prepared - $closed;

}

if( $isParent ) {

    $d1 = getDiff();

    $status = null;

    while ( count( $children)) {

        pcntl_wait( $status);

        array_pop( $children);

    }

    echo "Completed in " . ( microtime( true) - $start) . " seconds.\n";

    $d2 = getDiff();

    $leaked = $d2 - $d1;

    echo "D1: {$d1}, D2: {$d2}, Leaked: {$leaked}\n";

    die();

}

$endpoint = $type === 'maxscale' ? 'unix_socket=/tmp/maxscale.sock' : 'host=galera1';

$endpoint = 'host=127.0.0.1';

$dsn = "mysql:{$endpoint};dbname=wiseflow";

$options = array(

    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,

    PDO::ATTR_EMULATE_PREPARES => false,

    PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'UTF8'"

);

$dbh = new PDO( $dsn, 'queryuser', 'password', $options );

for( $i = 0; $i < $stmtCount; $i++ ) {

  //  echo "Preparing stmt $i\n";

    $param = 'Com_stmt_prepare';

    $stmt = $dbh->prepare( "show global status where variable_name = ?" );

    $stmt->bindParam( 1, $param, PDO::PARAM_STR );

    $stmt->execute();

    $res = $stmt->fetch( PDO::FETCH_ASSOC );

//    var_dump( $res );

}