Query Posts based on Variable Date Range

Hello. I am attempting to query all posts within a week of the current post.

[code moderated – please use the pastebin for any code over 10 lines]

Everything is functioning as expected, except for the variable $end_date in the filter_where function. When I replace the variable with the correct date (the same date the variable is returning) the page functions as it should.

Why would there not be an issue with the $post_date variable but one with the $end date?

Thanks.