search a word in a string...

my problem is that:
i have a string $phrase which is contain "Hello world. How are you? I'm fine..."

also i create a variable $look_word = "are"

and i want is that if the variable $look_word is in the string $phrase... is like a bit of comparasion...

please Help me!!!
Thanks

$present = substr_count(strtolower($phrase), strtolower($look_word));

if $present = "1"
1 occurance

thanks first of all.
hm...
if i want to find the last match word of the string...
can i do it??
thanks.

thanks...
you get the word but can i get the starting position of each word in that contain in this string?
thanks...