In mysql, I have the following information:

Article_Name Category_ID ------------- ----------- Penguins 20 Lions 20 Tigers 20 Electricity 21 Power Plants 21 Buddhism 22 

I want to count the number of articles, or I guess you call them "entries", with the Category_ID "20". Is there a function php function I can call to find the number of articles with Category_ID "20"?