%%[
var @fbTitle, @fbImage, @fbSummary, @fbURL, @fbPostURL
set @fbTitle = "this is the title"
set @fbImage = "https://www.google.com/images/srpr/logo3w.png"
set @fbSummary = "whee whoa whoops"
set @fbURL = "https://sprignaturemoves.com/"
set @fbPostURL = concat("https://www.facebook.com/sharer/sharer.php?s=100&p%5Btitle%5D=", urlencode(@fbTitle,1),"&p%5Burl%5D=",urlencode(@fbURL,1),"&p%5Bimages%5D%5B0%5D=",urlencode(@fbImage,1),"&p%5Bsummary%5D=",urlencode(@fbSummary,1))
]%%
<a href="%%=redirectto(@fbPostUrl)=%%">Post to Facebook</a>