How to increment through records on a weekly basis

I have results for a weekly time sheet that I have dynamically generated on a page. What i want to do is to be able to navigate through these records on a weekly basis. the code below is the query i use to generate the results. My question is...Is it possible to create a variable that would go forward or back in one week increments?

Is this done in the query? or do i need to set up some php variables that accomplish this and use them in the query? any help is appreciated.
-a

$week_query = ("SELECT * from timecard_data
		WHERE WEEK(CURDATE()) = WEEK(job_date) 
		AND emp_id = '$emp';");

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