Select records from today, this week, this month php mysql

Assuming your date column is an actual MySQL date column:

SELECT * FROM jokes WHERE date > DATE_SUB(NOW(), INTERVAL 1 DAY) ORDER BY score DESC;        
SELECT * FROM jokes WHERE date > DATE_SUB(NOW(), INTERVAL 1 WEEK) ORDER BY score DESC;
SELECT * FROM jokes WHERE date > DATE_SUB(NOW(), INTERVAL 1 MONTH) ORDER BY score DESC;

Try using date and time functions (MONTH(), YEAR(), DAY(), MySQL Manual)

This week:

SELECT * FROM jokes WHERE WEEKOFYEAR(date)=WEEKOFYEAR(NOW());

Last week:

SELECT * FROM jokes WHERE WEEKOFYEAR(date)=WEEKOFYEAR(NOW())-1;