How can I contain a PDO query in a PHP function? [duplicate]

I verified that a query works. If I try to contain a version of it in a function, it doesn't seem to work. Here is the query on its own; the verification of its functionality comes from the echo in the last line:

    $stmt = $conn->prepare('SELECT * FROM ObjectTable WHERE RowNum = ?');
    $stmt->execute([$objecttablerow]);
    while ($row = $stmt->fetch())
        {
    $objectformout = "${row['ObjectForm']}";
        }  
    echo $objectformout;

Here is my attempt to contain that query in a function; I was able to independently verify that $objecttablerow contains the expected integer value that a simple function can at least echo:

    function verbalize_object($vo_input) {
        $objectformout = "";
        $stmt = $conn->prepare('SELECT * FROM ObjectTable WHERE RowNum = ?');
        $stmt->execute([$vo_input]);
        while ($row = $stmt->fetch())
        {
            $objectformout = "${row['ObjectForm']}";
        }    
    return $objectformout;
    }

    echo verbalize_object($objecttablerow);

source https://stackoverflow.com/questions/70146168/how-can-i-contain-a-pdo-query-in-a-php-function