Plugin option default value

by

There are two errors in your code.

  1. "echo'plugins_url( '/image/top.png', __FILE__ )'" is not executed, it is just a string that happens to look like PHP code.
    What you really want is:

    $arr = array( "top_image"=> plugins_url( '/image/top.png', __FILE__ ) );

  2. Do not store default options in the database. Use the second parameter for get_option( $option, $default ); instead.

    So whenever you fetch the option, provide the default values as second argument:

    $option = get_option( 
    'scroll_options', 
    array( 
        "top_image"=> plugins_url( '/image/top.png', __FILE__ ) 
    ) 
);

    The reason is that you cannot rely on the stored values anyway. They might be deleted already, so you have to provide the default values always.