Only display a certain number of chars? (and other problems)

[Ember]

Ok, I am working on making a news script for a new site... I have currently come up with these problems:

I want to show a snippet of the news post on the main page, but how can i restrict the number of characters that are displayed?

For example - "Yadda Yadda has died today after an assasination in his home..."

I only want it to display a certain number of characters or words, or whatever I can restrict! Can anyone help me with that?

Also...

Can anyone tell me an effective way to have user comments on news posts, I thought of having a table called "comments" and then a "postid" field... and then displaying all the comments where the postid=1 or whatever, but how do I set postid from one table and then read it in another?

Please help me in as plain-english as possible, I havent been into this PHP stuff too long, I have made some scripts though, so I know a fair bit.

Thanks for your time!