I am pretty sure such an obvious question was answered before, but I was not able to find the right topic.
Lets say I have an "http" field in my form. I am using post template to make a post and publish it.
I want to have "Source: -http-" in the post, where -http- is the value of http-field.
The thing is http field is optional. So there can be no input at all. In such case I would not like to have just "Source: " printed on the page.
So how it is possible to display or hide code ("source: " in the case) based on whether there is anything in the http-field or not?