Display part of String

I am trying to set up a news page on my website where the first page has the Headline and then a snippet of the story.

I can get the content out of the database without any trouble but can't find out how to only read part of the large text string which is the story.

I know in VB I can use to get the first 100 characters fgrom the string.

<code>
strStoryPreview = ("story")
strStoryPreview = strStoryPreview.Substring(0,100)
</code>

but can't find a way to do in PHP.

Any advice would be much appreciated

Thank in advance.

Michael