MSSQL: SQLSTATE [] (null) (severity 0) after loading 1000 rows

I have some reports where I need to perform new SQL queries in the loop. These reports are running on PHP and datatables.

At times, when the number of rows reaches a volume greater than 1000, the MSSQL: SQLSTATE [] (null) (severity 0) error is displayed, aborting code execution.

Connection function:

 function pdo_mysql($sql){

    f_log($sql);

    $host = ***;
    $user = ***;
    $pass = ***;
    $db   = ***;

    try {
        $PDO = new PDO( 'mysql:host=' . $host . ';dbname=' . $db, $user, $pass );
    }
    catch ( PDOException $e ) {
        echo 'Erro ao conectar com o MySQL: ' . $e->getMessage(); exit;
    }

    $result = $PDO->query( $sql );

    if (is_array($result)){
        $row = $result->fetchAll( PDO::FETCH_ASSOC );
    }else{
        $row = $result;
    }

    return $row;

 }

Template of problem file:

$sql = "SELECT ....";
$return = pdo_mssql($sql);

foreach ($return as $row){

    $sql2 = "SELECT ...."
    $return = pdomssql($sql2);

    foreach ($return2 as $row2){
        // Guarda dados em variáveis.
    }

    $sql2 = "SELECT ...."
    $return = pdomssql($sql2);

    foreach ($return2 as $row2){
        // Guarda dados em variáveis.
    }

    $sql2 = "SELECT ...."
    $return = pdomssql($sql2);

    foreach ($return2 as $row2){
        // Guarda dados em variáveis.
    }

    // Exibe resultados

}

Has anyone ever had anything like this or do you have any suggestions?

Thank you