[support] help with php please

I have a custom module which replaces some asci characters with htlm equivalent for display on the webpages. I am exporting from a FileMaker database and importing via Feeds Module.

In my custom module I added this:

$node->field_book_title['und']['0']['value'] = str_replace("'","'",$node->field_book_title['und']['0']['value']);

and then get an error and cannot see the screen. I want to display an apostrophe in the appropriate places and thought I did it correctly but ...

I also want to replace "<br>" with a line break and now am afraid of trying that ... suggestions please.

thanks,

Pia